Schedule III - Real Estate and Accumulated Depreciation - Rollforward of Carrying Amount of Real Estate Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
SEC Schedule III, Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance as of the beginning of the year	$ 2,953,532	$ 2,561,073	$ 2,227,764
Acquisitions	266,747	410,732	308,229
Additions	28,828	33,109	27,787
Dispositions	(43,318)	(51,382)	(2,707)
Impairments	(926)	0	0
Balance as of the end of the year	3,204,863	2,953,532	2,561,073
Lease intangibles	430,749	$ 419,288	$ 411,900
Federal income tax basis	$ 3,600,000