Fair Value Measurements - Carrying Values and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	$ 20,310
Debt Instrument, Unamortized Discount	6,888
Mortgage Loans
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	13,900	$ 27,946
Debt Instrument, Unamortized Discount	0
Secured Term Loan
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	2,323	2,486
Debt Instrument, Unamortized Discount	0
Term Loan Facility
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	4,087	6,253
Debt Instrument, Unamortized Discount	0
Revolving Facility
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	0
Debt Instrument, Unamortized Discount	0
Convertible Senior Notes
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	0
Debt Instrument, Unamortized Discount	6,888	10,701
Fair Value \| Level 2
Assets carried at historical cost on the consolidated balance sheets
Investments in debt securities	312,661	318,299
Fair Value \| Mortgage Loans \| Level 2
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	6,181,214	6,292,261
Fair Value \| Secured Term Loan \| Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	461,617	411,213
Fair Value \| Term Loan Facility \| Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	1,499,446	1,500,444
Fair Value \| Convertible Senior Notes \| Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	352,103	346,489
Carrying Value \| Level 2
Assets carried at historical cost on the consolidated balance sheets
Investments in debt securities	309,122	316,991
Carrying Value \| Mortgage Loans \| Level 2
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	6,108,880	6,266,407
Carrying Value \| Secured Term Loan \| Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	403,363	403,464
Carrying Value \| Term Loan Facility \| Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	1,500,000	1,500,000
Carrying Value \| Convertible Senior Notes \| Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	$ 338,112	$ 334,299

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Amount, after accumulated amortization, of debt discount.

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- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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