Additional Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in operating assets and liabilities, net of effect of businesses acquired [Abstract]
Accounts receivable	$ (51,152)	$ (4,120)	$ (11,250)
Inventories	(55,062)	13,760	(30,302)
Prepaid expenses and other current assets	(3,668)	(12,180)	(5,203)
Accounts payable	42,291	17,839	(13,419)
Other current liabilities	21,184	(19,505)	32,925
Net change in operating assets and liabilities	$ (46,407)	$ (4,206)	$ (27,249)