Fair Value Measurements - Financial Assets and Liabilities, Recurring (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Assets
Deferred compensation plan	$ 13,013	$ 12,921
Derivative instruments	18,994	0
Liabilities
Deferred compensation plan	25,144	22,371
Recurring basis
Assets
Deferred compensation plan	13,013	12,921
Derivative instruments	18,994
Total assets	32,007	12,921
Liabilities
Deferred compensation plan	25,144	22,371
Total liabilities	25,144	22,371
Quoted Prices in Active Markets for Identical Assets (Level 1) | Recurring basis
Assets
Deferred compensation plan	13,013	12,921
Derivative instruments	0
Total assets	13,013	12,921
Liabilities
Deferred compensation plan	25,144
Total liabilities	25,144	22,371
Significant Other Observable Inputs (Level 2) | Recurring basis
Assets
Deferred compensation plan	0	0
Derivative instruments	15,347
Total assets	15,347	0
Liabilities
Deferred compensation plan	0	0
Total liabilities	0	0
Significant Unobservable Inputs (Level 3) | Recurring basis
Assets
Deferred compensation plan	0	0
Derivative instruments	3,647
Total assets	3,647	0
Liabilities
Deferred compensation plan	0	0
Total liabilities	$ 0	$ 0