Debt Obligations, net (Future Scheduled Maturities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Maturities of Long-term Debt [Abstract]
2020	$ 0
2021	159,083
2022	845,946
2023	491,875
2024	775,000
Thereafter	1,164,134
Total principal maturities	3,436,038	$ 3,661,617
Unamortized discounts and deferred financing costs, net	(48,958)	(52,531)
Total debt obligations, net	3,387,080	3,609,086
Unsecured Debt
Maturities of Long-term Debt [Abstract]
2020	0
2021	0
2022	798,045
2023	0
2024	775,000
Thereafter	650,000
Total principal maturities	2,223,045
Unamortized discounts and deferred financing costs, net	(41,228)
Total debt obligations, net	2,181,817
Unsecured Notes
Maturities of Long-term Debt [Abstract]
Total principal maturities	2,123,045	2,112,500
Unsecured Notes \| 5.00% senior notes
Maturities of Long-term Debt [Abstract]
Total principal maturities	0	375,000
Secured Debt
Maturities of Long-term Debt [Abstract]
2020	0
2021	159,083
2022	47,901
2023	491,875
2024	0
Thereafter	514,134
Total principal maturities	1,212,993	1,449,117
Unamortized discounts and deferred financing costs, net	(7,730)
Total debt obligations, net	1,205,263
Secured Debt \| 2015 $350 Million Revolving Credit Facility
Maturities of Long-term Debt [Abstract]
Total principal maturities	$ 0	$ 0

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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