Indebtedness and Derivative Financial Instruments - Maturity (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Maturity and Other
2019	$ 1,416,309
2020	1,972,316
2021	3,146,997
2022	3,596,138
2023	1,869,674
Thereafter	11,365,890
Total principal maturities	23,367,324
Net unamortized debt discount	(32,869)
Debt issuance costs, net	(96,175)	$ (110,734)
Other Debt Obligations	67,255	68,420
Total mortgages and unsecured indebtedness	23,305,535	24,632,463
Cash paid for interest	$ 811,971	$ 814,729	$ 887,118

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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