SEC Schedule III Rollforward of Real Estate Assets and Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]
Real estate, balance at beginning of period	$ 14,756,295	$ 14,187,820	$ 13,545,295
Additions during the period	16,592,044	14,807,938	14,430,294
Less: Assets sold, written-off and deconsolidated	354,161	51,643	242,474
Real estate, balance at end of period	16,237,883	14,756,295	14,187,820
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation [Roll Forward]
Accumulated depreciation, balance at beginning of period	2,885,283	2,581,514	2,356,728
Additions charged to operating expenses	381,500	360,391	346,755
Real estate accumulated depreciation	3,266,783	2,941,905	2,703,483
Less: Accumulated depreciation on assets sold, written-off and deconsolidated	86,608	56,622	121,969
Accumulated depreciation, balance at end of period	3,180,175	2,885,283	2,581,514
Land
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]
Additions during the period	170,065	21,298	30,805
Buildings & improvements
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]
Additions during the period	$ 1,665,684	$ 598,820	$ 854,194