Indebtedness and Derivative Financial Instruments - Maturity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Maturity and Other
2016	$ 2,928,580
2017	3,043,067
2018	1,024,275
2019	2,607,519
2020	3,159,632
Thereafter	9,739,204
Total principal maturities	22,502,277
Net unamortized debt premium	(104)
Total mortgages and unsecured indebtedness	22,502,173	$ 20,852,993
Cash paid for interest	$ 943,683	$ 1,018,911	$ 1,086,128