Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 34.4	$ 21.2
Other Comprehensive Income
Foreign currency translation	2.1	(2.6)
Pension and postretirement benefits liability adjustment (net of tax of $(1.3), $(1.7), respectively)	3.7	4.8
Total Other Comprehensive Income	5.8	2.2
Comprehensive Income	40.2	23.4
Less: comprehensive income attributable to noncontrolling interests, net of tax	0.2	0.0
Comprehensive Income attributable to Graybar Electric Company, Inc.	$ 40.0	$ 23.4