Fair Value Measurements - Financial Assets and Liabilities, Recurring (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Assets
Deferred compensation plan	$ 11,760	$ 12,921
Liabilities
Deferred compensation plan	24,522	22,371
Derivative instruments	19,731	0
Recurring basis
Assets
Deferred compensation plan	11,760	12,921
Total assets	11,760	12,921
Liabilities
Deferred compensation plan	24,522	22,371
Derivative instruments	19,495
Total liabilities	44,017	22,371
Quoted Prices in Active Markets for Identical Assets (Level 1) | Recurring basis
Assets
Deferred compensation plan	11,760	12,921
Total assets	11,760	12,921
Liabilities
Deferred compensation plan	24,522	22,371
Derivative instruments	0
Total liabilities	24,522	22,371
Significant Other Observable Inputs (Level 2) | Recurring basis
Assets
Deferred compensation plan	0	0
Total assets	0	0
Liabilities
Deferred compensation plan	0	0
Derivative instruments	11,189
Total liabilities	11,189	0
Significant Unobservable Inputs (Level 3) | Recurring basis
Assets
Deferred compensation plan	0	0
Total assets	0	0
Liabilities
Deferred compensation plan	0	0
Derivative instruments	8,306
Total liabilities	$ 8,306	$ 0