Fair Value Measurements - Carrying Amounts and Estimated Fair Values by Input Level (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jan. 19, 2017
Financial liabilities:
Interest rate	5.625%
Senior notes | 5.625% Notes
Financial liabilities:
Interest rate	5.625%		5.625%
Carrying Amount | Recurring
Financial assets:
Cash and cash equivalents	$ 378,766	$ 479,598
Held-to-maturity securities	7,466	7,466
Promissory notes	16,853	16,853
Financial liabilities:
Other liabilities	27,246	21,863
Carrying Amount | Recurring | Secured credit facility
Financial liabilities:
Long-term debt	2,056,100	1,907,932
Carrying Amount | Recurring | Senior notes | 5.625% Notes
Financial liabilities:
Long-term debt	399,374	399,332
Carrying Amount | Recurring | Other long-term obligations
Financial liabilities:
Long-term debt	96,644	104,583
Fair Value | Recurring
Financial assets:
Cash and cash equivalents	378,766	479,598
Held-to-maturity securities	7,763	7,879
Promissory notes	17,267	17,415
Financial liabilities:
Other liabilities	27,239	21,857
Fair Value | Recurring | Secured credit facility
Financial liabilities:
Long-term debt	2,081,977	1,886,333
Fair Value | Recurring | Senior notes | 5.625% Notes
Financial liabilities:
Long-term debt	399,500	360,000
Fair Value | Recurring | Other long-term obligations
Financial liabilities:
Long-term debt	89,405	96,338
Level 1 | Recurring
Financial assets:
Cash and cash equivalents	378,766	479,598
Held-to-maturity securities	0	0
Promissory notes	0	0
Financial liabilities:
Other liabilities	0	0
Level 1 | Recurring | Secured credit facility
Financial liabilities:
Long-term debt	2,081,977	1,886,333
Level 1 | Recurring | Senior notes | 5.625% Notes
Financial liabilities:
Long-term debt	399,500	360,000
Level 1 | Recurring | Other long-term obligations
Financial liabilities:
Long-term debt	0	0
Level 2 | Recurring
Financial assets:
Cash and cash equivalents	0	0
Held-to-maturity securities	7,763	7,879
Promissory notes	17,267	17,415
Financial liabilities:
Other liabilities	2,807	2,815
Level 2 | Recurring | Secured credit facility
Financial liabilities:
Long-term debt	0	0
Level 2 | Recurring | Senior notes | 5.625% Notes
Financial liabilities:
Long-term debt	0	0
Level 2 | Recurring | Other long-term obligations
Financial liabilities:
Long-term debt	89,405	96,338
Level 3 | Recurring
Financial assets:
Cash and cash equivalents	0	0
Held-to-maturity securities	0	0
Promissory notes	0	0
Financial liabilities:
Other liabilities	24,432	19,042
Level 3 | Recurring | Secured credit facility
Financial liabilities:
Long-term debt	0	0
Level 3 | Recurring | Senior notes | 5.625% Notes
Financial liabilities:
Long-term debt	0	0
Level 3 | Recurring | Other long-term obligations
Financial liabilities:
Long-term debt	$ 0	$ 0