Fair Value Measurements - Carrying Values and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	$ 66,544
Debt instrument, unamortized discount	19,912	$ 26,464
Mortgage Loans
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	56,682	28,075
Debt instrument, unamortized discount	0
Term Loan Facility
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	9,862
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	19,912	26,464
Term Loan Facility \| Revolving Facility
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	9,862	12,027
Carrying Value \| Level 2
Assets carried at historical cost on the consolidated balance sheets
Investments in debt securities	392,860	378,545
Carrying Value \| Mortgage Loans \| Level 2
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	7,466,382	7,608,228
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 \| Revolving facility \| Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	0	35,000
Carrying Value \| Convertible Senior Notes \| Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	555,081	548,536
Fair Value \| Level 2
Assets carried at historical cost on the consolidated balance sheets
Investments in debt securities	390,163	379,500
Fair Value \| Mortgage Loans \| Level 2
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	7,418,180	7,627,423
Fair Value \| Term Loan Facility \| Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	1,500,033	1,494,494
Fair Value \| Revolving facility \| Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	0	35,007
Fair Value \| Convertible Senior Notes \| Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	$ 548,305	$ 557,179

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- Definition

Amount, after accumulated amortization, of debt discount.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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-Publisher FASB
-Name Accounting Standards Codification
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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.

+ References

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