General - Effect of the Adoption of ASU 2014-09 and 2017-07 (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Effect on net sales	$ 1,894,066	$ 1,937,620	$ 5,825,803	$ 5,860,028
Effect on cost of sales	1,503,469	1,495,782	4,553,919	4,488,491
Effect on gross profit	390,597	441,838	1,271,884	1,371,537
Effect on selling and distribution	349,244	332,551	1,031,961	1,015,624
Effect on general and administrative	66,582	67,950	208,076	238,895
Effect on total operating costs and expenses	416,380	438,547	1,323,214	1,317,978
Effect on operating income	(25,783)	3,291	(51,330)	53,559
Effect on other (income) expense, net	$ 432	414	$ 1,684	805
Accounting Standards Update 2017-07
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Effect on cost of sales		(98)		(292)
Effect on gross profit		98		292
Effect on selling and distribution		(132)		(399)
Effect on general and administrative		(846)		(2,537)
Effect on total operating costs and expenses		(978)		(2,936)
Effect on operating income		1,076		3,228
Effect on other (income) expense, net		1,076		3,228
Pro Forma Results Assuming Retrospective Adoption of ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Effect on net sales		2,085,944		6,316,559
Effect on cost of sales		1,644,204		4,945,314
Effect on gross profit		441,740		1,371,245
Increase (Decrease) to Previously Reported Amounts | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Effect on net sales		148,324		456,531
Effect on cost of sales		148,324		456,531
Effect on gross profit		0		0
As Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Effect on net sales		1,937,620		5,860,028
Effect on cost of sales		1,495,880		4,488,783
Effect on gross profit		441,740		1,371,245
As Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Effect on cost of sales		1,495,880		4,488,783
Effect on gross profit		441,740		1,371,245
Effect on selling and distribution		332,683		1,016,023
Effect on general and administrative		68,796		241,432
Effect on total operating costs and expenses		439,525		1,320,914
Effect on operating income		2,215		50,331
Effect on other (income) expense, net		$ (662)		$ (2,423)