Schedule III - Real Estate and Accumulated Depreciation (Changes in Total Real Estate Assets and Accumulated Depreciation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule III - Real Estate and Accumulated Depreciation [Abstract]
Balance, beginning of period	$ 7,387,597	$ 6,998,233	$ 6,655,139
Acquisition of operating properties and unconsolidated joint ventures	0	0	61,736
Development and repositions	278,447	347,429	469,040
Improvements	65,892	66,640	52,000
Cost of real estate sold – other	(355,246)	(24,705)	(172,475)
Classification to held for sale	0	0	(67,207)
Balance, end of period	7,376,690	7,387,597	6,998,233
Balance, Beginning of period	1,780,694	1,557,004	1,477,147
Depreciation of real estate assets	243,403	233,955	213,964
Dispositions	(133,441)	(10,265)	(94,043)
Transfers to held for sale	0	0	(40,064)
Balance, End of period	1,890,656	$ 1,780,694	$ 1,557,004
Real Estate, Federal Income Tax Basis	$ 6,200,000