Debt (Summary of Debt) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Outstanding principal	$ 2,592,430
Deferred financing costs	(8,302)	$ (8,491)
Total debt	2,602,652	2,607,379
Debt classified as current	(3,131)	(3,008)
Long-term debt	2,599,521	2,604,371
Margin Loan Facility
Debt Instrument [Line Items]
Outstanding principal	1,300,000
Total debt	1,300,000	1,300,000
Senior notes
Debt Instrument [Line Items]
Outstanding principal	775,000
Total debt	793,524	796,138
Senior credit facility
Debt Instrument [Line Items]
Outstanding principal	510,822
Total debt	510,822	512,666
Wells Fargo note payable
Debt Instrument [Line Items]
Outstanding principal	6,608
Total debt	$ 6,608	$ 7,066

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

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