Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net Sales	$ 6,631,227	$ 6,385,032	$ 6,110,299
Cost of merchandise sold	(5,369,920)	(5,176,669)	(4,955,554)
Gross Margin	1,261,307	1,208,363	1,154,745
Selling, general and administrative expenses	(1,047,157)	(1,008,729)	(965,134)
Depreciation and amortization	(48,890)	(47,852)	(43,242)
Other income, net	6,545	5,347	8,199
Income from Operations	171,805	157,129	154,568
Interest expense, net	(4,257)	(3,630)	(2,227)
Income before Provision for Income Taxes	167,548	153,499	152,341
Provision for income taxes	(95,613)	(60,186)	(61,009)
Net Income	71,935	93,313	91,332
Net income attributable to noncontrolling interests	(327)	(234)	(264)
Net Income attributable to Graybar Electric Company, Inc.	$ 71,608	$ 93,079	$ 91,068
Net Income attributable to Graybar Electric Company, Inc. per share of Common Stock (usd per share)	$ 3.70	$ 4.87	$ 4.82