Indebtedness and Derivative Financial Instruments - Maturity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Maturity and Other
2017	$ 2,233,249
2018	802,806
2019	742,323
2020	3,563,396
2021	2,740,755
Thereafter	13,016,921
Total principal maturities	23,099,450
Net unamortized debt premium	(24,510)
Debt issuance costs, net	(97,836)	$ (85,491)
Total mortgages and unsecured indebtedness	22,977,104	22,416,682
Cash paid for interest	$ 887,118	$ 943,683	$ 1,018,911