Schedule III Part II - Summary of Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]
Aggregate cost basis for Federal tax purposes	$ 5,300,000
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements [Abstract]
Balance at beginning of year	5,608,998	$ 5,149,463	$ 4,779,674
Acquisitions	291,726	174,328	76,359
Improvements	281,471	329,674	329,522
Deduction during period—dispositions and retirements of property and transfer to joint venture	117,789	44,467	36,092
Balance at end of year	6,064,406	5,608,998	5,149,463
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at beginning of year	1,467,050	1,350,471	1,224,295
Additions during period—depreciation and amortization expense	156,513	155,662	147,730
Deductions during period—dispositions and retirements of property	49,522	39,083	21,554
Balance at end of year	$ 1,574,041	$ 1,467,050	$ 1,350,471