Fair Value Measurements - Financial Assets and Liabilities, Recurring (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets
Deferred compensation plan	$ 16,050	$ 14,966
Derivative instruments	4,474	2,239
Liabilities
Deferred compensation plan	27,849	29,145
Recurring basis
Assets
Deferred compensation plan	16,050	14,966
Derivative instruments	4,474	2,239
Total assets	20,524	17,205
Liabilities
Deferred compensation plan	27,849	29,145
Derivative instruments	10,651	30,637
Total liabilities	38,500	59,782
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Recurring basis
Assets
Deferred compensation plan	16,050	14,966
Derivative instruments	0	0
Total assets	16,050	14,966
Liabilities
Deferred compensation plan	27,849	29,145
Derivative instruments	0	0
Total liabilities	27,849	29,145
Significant Other Observable Inputs (Level 2) \| Recurring basis
Assets
Deferred compensation plan	0	0
Derivative instruments	577	0
Total assets	577	0
Liabilities
Deferred compensation plan	0	0
Derivative instruments	5,415	0
Total liabilities	5,415	0
Significant Unobservable Inputs (Level 3) \| Recurring basis
Assets
Deferred compensation plan	0	0
Derivative instruments	3,897	2,239
Total assets	3,897	2,239
Liabilities
Deferred compensation plan	0	0
Derivative instruments	5,236	30,637
Total liabilities	$ 5,236	$ 30,637

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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