Condensed Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Condensed Consolidated Statements Of Comprehensive Income [Abstract]
Net Income	$ 34.6	$ 49.0	$ 93.2	$ 130.4
Other Comprehensive Income
Foreign currency translation	2.2	(1.2)	(2.9)	3.0
Pension and postretirement benefits liability adjustment (net of tax of $(3.0), $(1.2), $(6.9) and $(3.7), respectively)	8.6	3.6	19.8	10.8
Total Other Comprehensive Income	10.8	2.4	16.9	13.8
Comprehensive Income	45.4	51.4	110.1	144.2
Less: Comprehensive income attributable to noncontrolling interests, net of tax	0.2	0.2	0.2	0.5
Comprehensive Income attributable to Graybar Electric Company, Inc.	$ 45.2	$ 51.2	$ 109.9	$ 143.7