Stockholders' Equity Repurchase Authorizations and Purchase Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		4 Months Ended	16 Months Ended	28 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock
Cash dividends declared on Class A and Class B common stock	$ 402	$ 337
Class A Common Stock
Class of Stock
Board authorization	18,500		$ 18,500	$ 18,500	$ 18,500
Dollar value of shares repurchased during period	1,383	$ 1,824
Remaining authorization	$ 6,921		6,921	6,921	$ 6,921	$ 8,304
Shares repurchased	4.7	8.7			50.1
Average price paid per share	$ 293.83	$ 209.05			$ 231.02
December 2018 Share Repurchase Plan | Class A Common Stock
Class of Stock
Board authorization							$ 6,500
Dollar value of shares repurchased during period	$ 304	$ 1,523
Remaining authorization	$ 0		0	$ 0	$ 0	304
Shares repurchased	1.0	7.1		25.8
Average price paid per share	$ 304.89	$ 213.68		$ 251.72
December 2017 Share Repurchase Plan | Class A Common Stock
Class of Stock
Board authorization								$ 4,000
Dollar value of shares repurchased during period	$ 0	$ 301
Remaining authorization	$ 0		0	$ 0	$ 0	0
Shares repurchased	0.0	1.6			20.6
Average price paid per share	$ 0	$ 188.38			$ 194.27
December 2019 Share Repurchase Plan [Member] | Class A Common Stock
Class of Stock
Board authorization						8,000
Dollar value of shares repurchased during period	$ 1,079
Remaining authorization	$ 6,921		$ 6,921	$ 6,921	$ 6,921	$ 8,000
Shares repurchased	3.7		3.7
Average price paid per share			$ 290.86
Common Stock
Class of Stock
Dividends per share (in dollars per share)	$ 0.40	$ 0.33
Common Stock | Class A Common Stock
Class of Stock
Shares repurchased	4.7
Retained Earnings
Class of Stock
Cash dividends declared on Class A and Class B common stock	$ 402	$ 337