CONDENSED CONSOLIDATED STATEMENTS OF EARNINGS - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Net sales	$ 2,893	$ 2,861	$ 5,692	$ 5,627
Cost of goods sold	1,772	1,750	3,476	3,424
Gross profit	1,121	1,111	2,216	2,203
Selling, general and administrative expenses	741	767	1,473	1,524
Operating earnings	380	344	743	679
Other income (expense):
Interest income	1	2	3	2
Interest expense	(22)	(23)	(43)	(48)
Other, net	7	1	14	(2)
Total other expense, net	(14)	(20)	(26)	(48)
Earnings before income taxes	366	324	717	631
Income taxes	94	76	183	142
Net earnings	272	248	534	489
Less: Net earnings attributable to noncontrolling interest	12	11	21	20
Net earnings attributable to W.W. Grainger, Inc.	$ 260	$ 237	$ 513	$ 469
Earnings per share:
Basic (in dollars per share)	$ 4.69	$ 4.19	$ 9.19	$ 8.29
Diluted (in dollars per share)	$ 4.67	$ 4.16	$ 9.14	$ 8.23
Weighted average number of shares outstanding:
Basic (in shares)	55,139,799	56,109,809	55,389,463	56,086,592
Diluted (in shares)	55,378,936	56,552,644	55,661,005	56,478,645
Cash dividends paid per share (in dollars per share)	$ 1.44	$ 1.36	$ 2.80	$ 2.64