Equity - Schedule of Repurchased Shares (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended												6 Months Ended			9 Months Ended			12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Repurchases of common stock (in shares)	3,661	3,730	4,170	5,871	1,863	3,991	6,298	4,105	3,498	3,642	3,916	3,911	10,041	10,403	7,828	13,771	14,394	11,469	17,432	16,257	14,967
Average Repurchase Price Per Share (in dollars per share)	$ 92.86	$ 91.16	$ 81.53	$ 74.95	$ 74.99	$ 75.17	$ 72.81	$ 73.08	$ 68.62	$ 65.90	$ 61.28	$ 58.49							$ 83.75	$ 73.71	$ 63.39
Amount of Repurchases	$ 340	$ 340	$ 340	$ 440	$ 139	$ 300	$ 459	$ 300	$ 240	$ 240	$ 240	$ 229							$ 1,460	$ 1,198	$ 949
Shares purchased	$ 540	$ 880	$ 1,220	$ 1,560	$ 2	$ 141	$ 441	$ 900	$ 51	$ 291	$ 531	$ 771	$ 1,220	$ 441	$ 531	$ 880	$ 141	$ 291	$ 540	$ 2	$ 51
Open Market
Class of Stock [Line Items]
Repurchases of common stock (in shares)																			1,300	2,200
Amount of Repurchases																			$ 100	$ 159
Rule 10b5-1 Trading Plan
Class of Stock [Line Items]
Repurchases of common stock (in shares)																			16,100	14,100
Amount of Repurchases																			$ 1,400	$ 1,000