Equity Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Balance Sheets:
Real estate properties, net	$ 4,938,862	$ 4,642,106
Acquired real estate leases, net	227,197	255,812
Cash and cash equivalents	428,373	222,449	77,520	102,219
Rents receivable, net	238,033	223,769
Other assets, net	206,204	188,675
Total assets	6,593,360	6,646,434
Revolving credit facility	235,000	235,000
Mortgage notes payable	895,231	914,510
Assumed real estate lease obligations, net	31,354	33,935
Other liabilities	138,412	165,855
Total liabilities and shareholders' equity	6,593,360	6,646,434
SIR
Balance Sheets:
Real estate properties, net	1,773,316	1,579,234
Acquired real estate leases, net	125,571	129,426
Cash and cash equivalents	20,804	20,025
Rents receivable, net	59,557	55,335
Other assets, net	17,643	17,839
Total assets	1,996,891	1,801,859
Revolving credit facility	74,000	159,000
Term loan	350,000	350,000
Mortgage notes payable	19,103	27,147
Assumed real estate lease obligations, net	27,020	26,966
Other liabilities	40,465	40,055
Shareholders' equity	1,486,303	1,198,691
Total liabilities and shareholders' equity	$ 1,996,891	$ 1,801,859