CONSOLIDATED STATEMENTS OF COMPREHENSIVE EARNINGS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net earnings	$ 895	$ 823	$ 623
Other comprehensive earnings (losses):
Foreign currency translation adjustments, net of reclassification (see Note 5 and Note 12)	26	(41)	93
Postretirement benefit plan re-measurement, net of tax expense $29 million (see Note 8 and Note 12)	0	0	47
Postretirement benefit plan reclassification, net of tax benefit of $2 million, $3 million and $1 million, respectively	(6)	(7)	2
Total other comprehensive (losses) earnings	20	(48)	142
Comprehensive earnings, net of tax	915	775	765
Less: Comprehensive earnings (losses) attributable to noncontrolling interest
Net earnings	46	41	37
Foreign currency translation adjustments	3	3	4
Total comprehensive earnings (losses) attributable to noncontrolling interest	49	44	41
Comprehensive earnings attributable to W.W. Grainger, Inc.	$ 866	$ 731	$ 724