Fair Value (Assets and Liabilities Not Measured at Fair Value) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Assets:
Cash and Restricted cash	$ 1,448,569	$ 1,242,997	$ 1,090,501	$ 620,135
Liabilities:
Variable-rate debt	1,397,881	1,945,344
Allowance for accounts receivable	29,900	33,000
Unamortized deferred financing costs	(45,100)	(32,800)
Notes receivable
Liabilities:
Allowance for notes receivable	200	200
Fair Value Hierarchy Level 1 | Carrying Amount
Assets:
Cash and Restricted cash	1,448,569	1,242,997
Fair Value Hierarchy Level 1 | Estimated Fair Value
Assets:
Cash and Restricted cash	1,448,569	1,242,997
Fair Value Hierarchy Level 3 | Carrying Amount
Assets:
Accounts receivable, net	81,935	66,726
Notes receivable, net	5,536	622
Fair Value Hierarchy Level 3 | Estimated Fair Value
Assets:
Accounts receivable, net	81,935	66,726
Notes receivable, net	5,536	622
Fair Value Hierarchy Level 2 | Carrying Amount
Liabilities:
Fixed-rate debt	2,795,832	2,374,822
Variable-rate debt	1,672,881	1,945,344
Fair Value Hierarchy Level 2 | Estimated Fair Value
Liabilities:
Fixed-rate debt	2,838,696	2,461,155
Variable-rate debt	$ 1,672,881	$ 1,945,344