Employer Sponsored Benefit Plans - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Cost of sales	$ 150,286	$ 131,552	$ 302,439	$ 256,541
Selling, product development and administrative expenses	23,878	23,290	49,349	48,640
Expected employer contributions during remainder of fiscal year	7,000		7,000
Contributions made by company to domestic pension plan	$ 3,000	1,200	$ 4,200	2,400
Accounting Standards Update 2017-07
Defined Benefit Plan Disclosure [Line Items]
Cost of sales		100		200
Selling, product development and administrative expenses		$ 100		$ 200