Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies (Details 2)

v3.8.0.1
Summary of Significant Accounting Policies (Details 2) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Change in Accounting Estimate [Line Items]      
Approximate amount by which basis of assets and liabilities for tax reporting purposes is higher than amount reported on consolidated balance sheet $ 150,000    
Deferred lease related compensation costs 1,100 $ 1,100 $ 1,200
Future minimum payments due $ 90,832    
Common Shares [Member]      
Change in Accounting Estimate [Line Items]      
Ordinary income (as a percent) 86.50% 48.00% 38.30%
Long-term capital gain (as a percent) 0.00% 0.00% 61.70%
Return of capital (as a percent) 13.50% 52.00% 0.00%
Preferred Shares [Member]      
Change in Accounting Estimate [Line Items]      
Ordinary income (as a percent) 100.00% 100.00% 38.30%
Long-term capital gain (as a percent) 0.00% 0.00% 61.70%
Return of capital (as a percent) 0.00% 0.00% 0.00%
Ground Leases [Member]      
Change in Accounting Estimate [Line Items]      
Future minimum payments due $ 89,900    
Accounting Standards Update 2017-05 [Member]      
Change in Accounting Estimate [Line Items]      
Effect of change on net income   $ 18,000