Condensed Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Condensed Consolidated Statements Of Income [Abstract]
Net sales	$ 1,900.5	$ 1,773.2
Cost of merchandise sold	(1,539.6)	(1,432.8)
Gross Margin	360.9	340.4
Selling, general and administrative expenses	(277.9)	(290.1)
Depreciation and amortization	(12.2)	(13.2)
Other income, net	0.5	0.6
Income from Operations	71.3	37.7
Non-operating expenses	(7.8)	(7.5)
Income before Provision for Income Taxes	63.5	30.2
Provision for income taxes	(16.2)	(8.7)
Net Income	47.3	21.5
Net income attributable to noncontrolling interests	(0.1)	(0.1)
Net Income attributable to Graybar Electric Company, Inc.	$ 47.2	$ 21.4
Net Income attributable to Graybar Electric Company, Inc. per share of Common Stock	$ 2.07	$ 0.94
Cash Dividends per share of Common Stock	$ 0.30	$ 0.30
Average Common Shares Outstanding	22.8	22.7