Stock Plans - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares Subject to Option
Beginning balance (in shares)		43,818,830	48,434,655	53,601,612
Options granted (in shares)		4,861,990	5,834,836	6,175,020
Options exercised (in shares)	[1]	(13,668,354)	(9,333,271)	(9,431,009)
Options cancelled (in shares)		(1,156,518)	(1,117,390)	(1,910,968)
Ending balance (in shares)		33,855,948	43,818,830	48,434,655
Exercisable at end of the period (in shares)		25,121,711
Weighted- Average Exercise or Grant Price Per Share
Beginning balance (in dollars per share)		$ 32.36	$ 29.92	$ 28.02
Options granted (in dollars per share)		47.76	43.16	43.18
Options exercised (in dollars per share)		27.53	25.16	26.17
Options cancelled (in dollars per share)		42.22	42.93	38.10
Ending balance (in dollars per share)		36.19	$ 32.36	$ 29.92
Exercisable at end of the period (in dollars per share)		$ 32.89
Average Remaining Contractual Term
Ending balance		5 years
Exercisable at end of the period		4 years
Aggregate Intrinsic Value
Options exercised		$ 306	$ 170	$ 170
Aggregate intrinsic value		640	371	626	$ 874
Exercisable at end of the period		557
Cash received from options exercised		369	231	257
Actual tax benefit realized for the tax deductions from the option exercises		$ 40	$ 21	$ 31
Annual grant to eligible employees
Shares Subject to Option
Options granted (in shares)		4,793,570	5,666,530	6,012,140
Weighted- Average Exercise or Grant Price Per Share
Options granted (in dollars per share)		$ 47.72	$ 43.51	$ 43.20
Additional options issued
Shares Subject to Option
Options granted (in shares)		68,420	168,306	162,880
Weighted- Average Exercise or Grant Price Per Share
Options granted (in dollars per share)		$ 50.82	$ 31.40	$ 42.54

[1] Cash received from options exercised was $369 million in 2019, $231 million in 2018 and $257 million in 2017. The actual tax benefit realized and recorded in the provision for income taxes for the tax deductions from the option exercises totaled $40 million in 2019, $21 million in 2018 and $31 million in 2017.