Equity Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Balance Sheets:
Real estate properties, net	$ 4,642,106	$ 6,821,803
Acquired real estate leases, net	255,812	427,756
Cash and cash equivalents	222,449	102,219	192,763	194,040
Rents receivable, net	223,769	253,394
Other assets, net	188,675	211,293
Total assets	6,646,434	8,189,634
Revolving credit facility	235,000	297,000
Mortgage notes payable	914,510	984,827
Assumed real estate lease obligations, net	33,935	69,304
Other liabilities	165,855	194,184
Shareholders' equity	3,363,586	3,105,428
Total liabilities and shareholders' equity	6,646,434	8,189,634
SIR
Balance Sheets:
Real estate properties, net	1,579,234	1,249,081
Acquired real estate leases, net	129,426	95,248
Cash and cash equivalents	20,025	20,373
Rents receivable, net	55,335	38,885
Other assets, net	17,839	27,065
Total assets	1,801,859	1,430,652
Revolving credit facility	159,000	95,000
Term loan	350,000	350,000
Mortgage notes payable	27,147	27,778
Assumed real estate lease obligations, net	26,966	20,434
Other liabilities	40,055	37,257
Shareholders' equity	1,198,691	900,183
Total liabilities and shareholders' equity	1,801,859	1,430,652
GOV
Balance Sheets:
Real estate properties, net		1,311,202
Assets of discontinued operations		47,142
Acquired real estate leases, net		144,402
Cash and cash equivalents		5,255
Rents receivable, net		28,882
Other assets, net		25,251
Total assets		1,562,134
Revolving credit facility		49,500
Term loan		350,000
Mortgage notes payable		93,127
Liabilities of discontinued operations		298
Assumed real estate lease obligations, net		19,129
Other liabilities		22,629
Shareholders' equity		1,027,451
Total liabilities and shareholders' equity		$ 1,562,134