Fair Value Measurements - Assets and Liabilities on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets
Deferred compensation plan	$ 14,699	$ 14,966
Derivative instruments	60,105	2,239
Total assets	74,804	17,205
Liabilities
Deferred compensation plan	25,780	29,145
Derivative instruments	2,440	30,637
Total liabilities	28,220	59,782
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Deferred compensation plan	14,699	14,966
Derivative instruments	0	0
Total assets	14,699	14,966
Liabilities
Deferred compensation plan	25,780	29,145
Derivative instruments	0	0
Total liabilities	25,780	29,145
Recurring Basis | Significant Other Observable Inputs (Level 2)
Assets
Deferred compensation plan	0	0
Derivative instruments	35,689	0
Total assets	35,689	0
Liabilities
Deferred compensation plan	0	0
Derivative instruments	0	0
Total liabilities	0	0
Recurring Basis | Significant Unobservable Inputs (Level 3)
Assets
Deferred compensation plan	0	0
Derivative instruments	24,416	2,239
Total assets	24,416	2,239
Liabilities
Deferred compensation plan	0	0
Derivative instruments	2,440	30,637
Total liabilities	$ 2,440	$ 30,637