Condensed Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Condensed Consolidated Statements Of Income [Abstract]
Net sales		$ 1,773.2	$ 1,777.8
Cost of merchandise sold		(1,432.8)	(1,439.1)
Gross Margin		340.4	338.7
Selling, general and administrative expenses		(290.1)	(273.5)
Depreciation and amortization		(13.2)	(12.5)
Other income, net		0.6	1.3
Income from Operations		37.7	54.0
Non-operating expenses		(7.5)	(6.6)
Income before Provision for Income Taxes		30.2	47.4
Provision for income taxes		(8.7)	(13.0)
Net Income		21.5	34.4
Net income attributable to noncontrolling interests		(0.1)	(0.1)
Net Income attributable to Graybar Electric Company, Inc.		$ 21.4	$ 34.3
Net Income attributable to Graybar Electric Company, Inc. per share of Common Stock (usd per share)	[1]	$ 0.94	$ 1.51
Cash Dividends per share of Common Stock		$ 0.30	$ 0.30
Average common shares outstanding	[1]	22.7	22.7

[1] Adjusted for the declaration of a 5% stock dividend in 2019, shares related to which were issued in February 2020.  Prior to the adjustment, the average common shares outstanding were 21.6 million for the three months ended March 31, 2019.