Fair Value Measurements - Financial Assets and Liabilities, Recurring (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
Deferred compensation plan	$ 15,717	$ 14,966
Derivative instruments	11,950	2,239
Liabilities
Deferred compensation plan	27,605	29,145
Recurring basis
Assets
Deferred compensation plan	15,717	14,966
Derivative instruments	11,313	2,239
Total assets	27,030	17,205
Liabilities
Deferred compensation plan	27,605	29,145
Derivative instruments	8,002	30,637
Total liabilities	35,607	59,782
Quoted Prices in Active Markets for Identical Assets (Level 1) | Recurring basis
Assets
Deferred compensation plan	15,717	14,966
Derivative instruments	0	0
Total assets	15,717	14,966
Liabilities
Deferred compensation plan	27,605	29,145
Derivative instruments	0	0
Total liabilities	27,605	29,145
Significant Other Observable Inputs (Level 2) | Recurring basis
Assets
Deferred compensation plan	0	0
Derivative instruments	3,326	0
Total assets	3,326	0
Liabilities
Deferred compensation plan	0	0
Derivative instruments	0	0
Total liabilities	0	0
Significant Unobservable Inputs (Level 3) | Recurring basis
Assets
Deferred compensation plan	0	0
Derivative instruments	7,987	2,239
Total assets	7,987	2,239
Liabilities
Deferred compensation plan	0	0
Derivative instruments	8,002	30,637
Total liabilities	$ 8,002	$ 30,637