Segments (Schedule of net sales, adjusted EBITDA and certain other measures by reportable segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net sales	$ 859,521	$ 990,264	$ 998,461	$ 834,202	$ 840,881	$ 881,012	$ 886,375	$ 757,700	$ 3,682,448	$ 3,365,968	$ 3,093,743
Gross profit	229,230	$ 241,303	$ 239,599	$ 199,084	196,086	$ 209,545	$ 211,687	$ 178,197	909,216	795,515	741,965
Depreciation & amortization									65,388	69,217	68,680
Total assets	1,576,111				1,473,350				1,576,111	1,473,350	1,395,014
Operating segments [Member] | Geographic divisions [Member]
Segment Reporting Information [Line Items]
Net sales									3,682,448	3,365,968	3,093,743
Gross profit									909,216	795,515	741,965
Depreciation & amortization									63,381	66,809	66,592
Adjusted EBITDA									340,464	250,061	244,616
Total assets	1,405,940				1,435,970				1,405,940	1,435,970	1,345,475
Other reconciling items [Member] | Other reconciling items [Member]
Segment Reporting Information [Line Items]
Net sales									0	0	0
Gross profit									0	0	0
Depreciation & amortization									2,007	2,408	2,088
Adjusted EBITDA									(74,585)	(50,058)	(50,726)
Total assets	$ 170,171				$ 37,380				$ 170,171	$ 37,380	$ 49,539