Equity Investments (Details2) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009
Balance Sheets:
Real estate properties, net	$ 5,964,475	$ 5,506,997
Acquired real estate leases, net	287,241	233,913
Cash and cash equivalents	55,035	194,040	33,443	18,204
Rents receivable	203,304	191,237
Other assets, net	224,837	171,380
Total assets	6,959,999	6,588,539
Revolving credit facility	230,000
Mortgage notes payable	380,597	351,526
Assumed real estate lease obligations, net	69,836	65,940
Other liabilities	137,357	123,842
Shareholders' equity	3,388,174	3,131,690
Total liabilities and shareholders' equity	6,959,999	6,588,539
GOV
Balance Sheets:
Real estate properties, net	1,036,462	846,447
Acquired real estate leases, net	80,075	60,097
Cash and cash equivalents	1,081	2,437
Rents receivable	21,200	19,200
Other assets, net	23,916	23,107
Total assets	1,162,734	951,288
Revolving credit facility	338,000	118,000
Mortgage notes payable	45,898	46,428
Assumed real estate lease obligations, net	12,626	13,679
Other liabilities	20,945	15,784
Shareholders' equity	745,265	757,397
Total liabilities and shareholders' equity	$ 1,162,734	$ 951,288