Segments (Schedule of net sales, adjusted EBITDA and certain other measures by reportable segment) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Net sales	$ 964,249	$ 990,264	$ 2,736,029	$ 2,822,927
Gross profit	254,767	241,303	716,666	679,986
Depreciation & amortization	18,535	16,626	52,959	48,560
Operating segments [Member] \| Geographic divisions [Member]
Segment Reporting Information [Line Items]
Net sales	964,249	990,264	2,736,029	2,822,927
Gross profit	254,767	241,303	716,666	679,986
Depreciation & amortization	17,974	16,106	51,121	47,079
Adjusted EBITDA	96,752	92,698	260,537	252,873
Other reconciling items [Member] \| Other reconciling items [Member]
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Gross profit	0	0	0	0
Depreciation & amortization	561	520	1,838	1,481
Adjusted EBITDA	$ (22,094)	$ (18,330)	$ (58,150)	$ (52,496)

Adjusted Earnings Before Interest, Taxes, Depreciation and Amortization and other items

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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1,2)
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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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