Equity Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Balance Sheets:
Real estate properties, net	$ 4,757,038	$ 6,821,803
Acquired real estate leases, net	272,381	427,756
Cash and cash equivalents	165,990	102,219	72,680	192,763
Rents receivable, net	218,301	253,394
Other assets, net	195,330	211,293
Total assets	6,821,987	8,189,634
Revolving credit facility	235,000	297,000
Mortgage notes payable	925,120	984,827
Assumed real estate lease obligations, net	38,087	69,304
Other liabilities	169,498	194,184
Shareholders' equity	3,421,033	3,105,428
Total liabilities and shareholders' equity	6,821,987	8,189,634
SIR
Balance Sheets:
Real estate properties, net	1,510,338	1,249,081
Acquired real estate leases, net	114,937	95,248
Cash and cash equivalents	14,540	20,373
Rents receivable, net	52,174	38,885
Other assets, net	23,162	27,065
Total assets	1,715,151	1,430,652
Revolving credit facility	80,000	95,000
Term loan	350,000	350,000
Mortgage notes payable	27,309	27,778
Assumed real estate lease obligations, net	19,317	20,434
Other liabilities	40,999	37,257
Shareholders' equity	1,197,526	900,183
Total liabilities and shareholders' equity	$ 1,715,151	$ 1,430,652