Fair Value Measurements - Financial Assets and Liabilities, Recurring (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets
Deferred compensation plan	$ 14,336	$ 12,587
Derivative instruments	6,605	2,991
Liabilities
Deferred compensation plan	27,598	24,169
Derivative instruments	800	40,259
Recurring basis
Assets
Deferred compensation plan	14,336	12,587
Derivative instruments	6,605	2,991
Total assets	20,941	15,578
Liabilities
Deferred compensation plan	27,598	24,169
Derivative instruments	1,106	40,259
Total liabilities	28,704	64,428
Quoted Prices in Active Markets for Identical Assets (Level 1) | Recurring basis
Assets
Deferred compensation plan	14,336	12,587
Derivative instruments	0	0
Total assets	14,336	12,587
Liabilities
Deferred compensation plan	27,598	24,169
Derivative instruments	0	0
Total liabilities	27,598	24,169
Significant Other Observable Inputs (Level 2) | Recurring basis
Assets
Deferred compensation plan	0	0
Derivative instruments	0	0
Total assets	0	0
Liabilities
Deferred compensation plan	0	0
Derivative instruments	178	21,400
Total liabilities	178	21,400
Significant Unobservable Inputs (Level 3) | Recurring basis
Assets
Deferred compensation plan	0	0
Derivative instruments	6,605	2,991
Total assets	6,605	2,991
Liabilities
Deferred compensation plan	0	0
Derivative instruments	928	18,859
Total liabilities	$ 928	$ 18,859