Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Current derivative asset		$ 10,985	$ 23,374
Long-term derivative asset	[1]	5,715
Total derivative instruments		16,700
Current derivative liability		38,483	$ 62,350
Long-term derivative liability	[2]	6,756
Total derivative instruments		45,239
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Current derivative asset		10,985
Long-term derivative asset	[1]	5,715
Total derivative instruments		16,700
Current derivative liability		38,483
Long-term derivative liability	[2]	6,756
Total derivative instruments		$ 45,239

[1] Included in Other assets in the Condensed Consolidated Balance Sheet.

[2] Included in Other long-term obligations in the Condensed Consolidated Balance Sheet.