Revenue (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue
Disaggregated sales	$ 2,482,975	$ 2,666,528	$ 2,589,874	$ 2,410,608	$ 2,314,957	$ 2,482,717	$ 2,456,073	$ 2,282,681	$ 10,149,985	$ 9,536,428	$ 8,977,726
DIY customer [Member]
Disaggregation of Revenue
Disaggregated sales									5,612,390	5,351,035	5,113,288
Professional service provider customer [Member]
Disaggregation of Revenue
Disaggregated sales									4,369,541	4,035,898	3,724,220
Other sales and sales adjustments [Member]
Disaggregation of Revenue
Disaggregated sales									$ 168,054	$ 149,495	$ 140,218