Revenue (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue
Disaggregated sales	$ 2,589,874	$ 2,456,073	$ 5,000,482	$ 4,738,754
DIY customer [Member]
Disaggregation of Revenue
Disaggregated sales	1,434,146	1,372,583	2,771,175	2,644,997
Professional service provider customer [Member]
Disaggregation of Revenue
Disaggregated sales	1,113,485	1,042,390	2,152,266	2,017,399
Other customers and sales adjustments [Member]
Disaggregation of Revenue
Disaggregated sales	$ 42,243	$ 41,100	$ 77,041	$ 76,358

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration