Information by Business Segment (Details) (USD $) In Thousands, unless otherwise specified
|
12 Months Ended |
Dec. 31, 2013
segment
|
Dec. 31, 2012
|
Dec. 31, 2011
|
Segment Reporting [Abstract] |
|
|
|
Number of primary office property segments (in number of segments) |
10
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
$ 498,633
|
$ 493,100
|
$ 495,832
|
Property operating expenses |
180,704
|
180,735
|
187,820
|
NOI from real estate operations |
317,929
|
312,365
|
308,012
|
Segment assets |
3,629,952
|
3,653,759
|
|
Operating Segment Total
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
498,633
|
493,100
|
495,832
|
Property operating expenses |
180,704
|
180,735
|
187,820
|
NOI from real estate operations |
317,929
|
312,365
|
308,012
|
Additions to long-lived assets |
56,877
|
106,801
|
105,109
|
Transfers from non-operating properties |
264,290
|
220,997
|
144,388
|
Segment assets |
2,905,630
|
2,945,930
|
3,039,440
|
Baltimore and Washington Corridor
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
237,869
|
238,488
|
237,162
|
Property operating expenses |
80,554
|
83,050
|
86,782
|
NOI from real estate operations |
157,315
|
155,438
|
150,380
|
Additions to long-lived assets |
28,087
|
25,921
|
33,142
|
Transfers from non-operating properties |
50,105
|
65,108
|
67,752
|
Segment assets |
1,243,099
|
1,267,357
|
1,350,678
|
Northern Virginia
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
92,010
|
79,574
|
74,214
|
Property operating expenses |
31,973
|
29,103
|
28,518
|
NOI from real estate operations |
60,037
|
50,471
|
45,696
|
Additions to long-lived assets |
13,090
|
65,157
|
14,770
|
Transfers from non-operating properties |
61,434
|
44,250
|
4
|
Segment assets |
616,082
|
569,860
|
484,392
|
San Antonio
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
33,060
|
32,018
|
30,066
|
Property operating expenses |
17,631
|
16,499
|
14,371
|
NOI from real estate operations |
15,429
|
15,519
|
15,695
|
Additions to long-lived assets |
335
|
280
|
0
|
Transfers from non-operating properties |
0
|
468
|
17,638
|
Segment assets |
118,299
|
119,369
|
131,412
|
Huntsville
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
5,050
|
3,867
|
1,368
|
Property operating expenses |
1,282
|
689
|
226
|
NOI from real estate operations |
3,768
|
3,178
|
1,142
|
Additions to long-lived assets |
3,563
|
26
|
26,837
|
Transfers from non-operating properties |
48,799
|
0
|
0
|
Segment assets |
77,773
|
28,730
|
32,341
|
Washington, DC - Capitol Riverfront
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
16,863
|
16,697
|
17,878
|
Property operating expenses |
7,844
|
7,555
|
6,762
|
NOI from real estate operations |
9,019
|
9,142
|
11,116
|
Additions to long-lived assets |
2,604
|
317
|
2,794
|
Transfers from non-operating properties |
0
|
0
|
0
|
Segment assets |
98,962
|
104,544
|
111,318
|
St. Mary's and King George Counties
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
16,568
|
16,392
|
14,366
|
Property operating expenses |
5,028
|
4,745
|
4,142
|
NOI from real estate operations |
11,540
|
11,647
|
10,224
|
Additions to long-lived assets |
2,341
|
1,844
|
1,638
|
Transfers from non-operating properties |
14
|
289
|
16,858
|
Segment assets |
96,143
|
98,027
|
100,818
|
Greater Baltimore
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
42,653
|
52,616
|
70,668
|
Property operating expenses |
16,583
|
19,917
|
29,543
|
NOI from real estate operations |
26,070
|
32,699
|
41,125
|
Additions to long-lived assets |
2,913
|
9,690
|
21,086
|
Transfers from non-operating properties |
360
|
37,558
|
16,307
|
Segment assets |
303,823
|
320,548
|
402,067
|
Greater Philadelphia
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
11,924
|
9,698
|
7,458
|
Property operating expenses |
3,431
|
2,562
|
1,402
|
NOI from real estate operations |
8,493
|
7,136
|
6,056
|
Additions to long-lived assets |
406
|
286
|
516
|
Transfers from non-operating properties |
28,034
|
10,626
|
5,446
|
Segment assets |
104,657
|
78,798
|
102,572
|
Colorado Springs
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
25,290
|
24,987
|
23,675
|
Property operating expenses |
9,002
|
9,231
|
8,758
|
NOI from real estate operations |
16,288
|
15,756
|
14,917
|
Additions to long-lived assets |
2,940
|
2,929
|
4,085
|
Transfers from non-operating properties |
5,438
|
4,295
|
214
|
Segment assets |
0
|
175,830
|
181,384
|
Other
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
10,075
|
12,116
|
13,923
|
Property operating expenses |
1,016
|
2,569
|
3,887
|
NOI from real estate operations |
9,059
|
9,547
|
10,036
|
Additions to long-lived assets |
0
|
152
|
182
|
Transfers from non-operating properties |
0
|
394
|
0
|
Segment assets |
80,002
|
82,090
|
98,808
|
Operating Wholesale Data Center
|
|
|
|
Segment financial information for real estate operations |
|
|
|
Revenues from real estate operations |
7,271
|
6,647
|
5,054
|
Property operating expenses |
6,360
|
4,815
|
3,429
|
NOI from real estate operations |
911
|
1,832
|
1,625
|
Additions to long-lived assets |
598
|
199
|
59
|
Transfers from non-operating properties |
70,106
|
58,009
|
20,169
|
Segment assets |
$ 166,790
|
$ 100,777
|
$ 43,650
|