Indebtedness - Future Principal Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
2020	$ 475,707
2021	14,420
2022	625,518
2023	143,784
2024	350,000
Thereafter	776,780
Total	2,386,209	$ 3,311,262
Unamortized debt premiums, discounts and issuance costs	(45,756)	(56,372)
Total debt outstanding	$ 2,340,453	$ 3,254,890

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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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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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