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Subsequent Events Subsequent Events (Details) (USD $)
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0 Months Ended | 0 Months Ended | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
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Jun. 30, 2012
|
Dec. 31, 2011
|
Aug. 06, 2012
Series G Preferred Stock [Member]
Call for Preferred Stock Redemption
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Jul. 23, 2012
Properties in Baltimore-Washington Corridor and Greater Baltimore [Member]
Discontinued Operation or Asset Disposal
acre
sqft
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Jul. 24, 2012
Properties in Baltimore-Washington Corridor and Greater Baltimore [Member]
Discontinued Operation or Asset Disposal
Property
|
Jul. 23, 2012
Interest rate swap one, effective date September 2, 2014
Designated as Hedging Instrument [Member]
Interest rate swaps
|
Jul. 23, 2012
Interest rate swap two, effective date September 2, 2014
Designated as Hedging Instrument [Member]
Interest rate swaps
|
Jul. 23, 2012
Interest rate swap one, effective date September 1, 2015
Designated as Hedging Instrument [Member]
Interest rate swaps
|
Jul. 23, 2012
Interest rate swap two, effective date September 1, 2015
Designated as Hedging Instrument [Member]
Interest rate swaps
|
Jul. 11, 2012
13587 McLearen Road
Acquisition
sqft
|
|
| Subsequent Event [Line Items] | ||||||||||
| Notional Amount | $ 100,000,000 | $ 100,000,000 | $ 100,000,000 | $ 100,000,000 | ||||||
| Fixed rate (as a percent) | 0.8055% | 0.81% | 1.673% | 1.73% | ||||||
| Floating rate index | One-Month LIBOR | One-Month LIBOR | One-Month LIBOR | One-Month LIBOR | ||||||
| Square footage of real estate properties (in square feet) | 1,400,000 | 202,000 | ||||||||
| Acquired property, percentage leased | 100.00% | |||||||||
| Cost of acquired property | 49,000,000 | |||||||||
| Number of real estate operating properties sold | 23 | |||||||||
| Acres of land parcel sold | 6 | |||||||||
| Sales price of properties sold | 162,000,000 | |||||||||
| Preferred stock, liquidation preference per share | $ 25.00 | |||||||||
| Preferred stock, liquidation preference value in aggregate | $ 388,833,000 | $ 216,333,000 | $ 55,000,000 | |||||||