FAIR VALUE (Assets and Liabilities Measured on a Nonrecurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Assets:
Cash and restricted cash	$ 736,369	$ 964,300	$ 868,274	$ 915,139
Liabilities:
Variable-rate debt:	1,520,577	1,350,914
Allowance for doubtful accounts	8,000	9,300
Allowance for notes receivable	100	100
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Carrying Amount
Assets:
Cash and restricted cash	685,908	914,165
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Estimated Fair Value
Assets:
Cash and restricted cash	685,908	914,165
Recurring | Significant Other Observable Inputs (Level 2) | Carrying Amount
Liabilities:
Fixed-rate debt:	1,643,194	1,526,875
Variable-rate debt:	1,520,577	1,350,914
Recurring | Significant Other Observable Inputs (Level 2) | Estimated Fair Value
Liabilities:
Fixed-rate debt:	1,622,249	1,554,766
Variable-rate debt:	1,520,577	1,350,914
Recurring | Significant Unobservable Inputs (Level 3) | Carrying Amount
Assets:
Accounts receivable, net	13,471	13,041
Notes receivable, net	4,085	5,864
Recurring | Significant Unobservable Inputs (Level 3) | Estimated Fair Value
Assets:
Accounts receivable, net	13,471	13,041
Notes receivable, net	$ 4,085	$ 5,864