Shareholders' Equity - Shares Repurchased (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended						6 Months Ended		7 Months Ended	12 Months Ended	79 Months Ended
	Aug. 07, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Aug. 07, 2019	Dec. 31, 2018	Aug. 07, 2019	Feb. 27, 2019
Equity, Class of Treasury Stock [Line Items]
Repurchases of common stock								$ 190	$ 250
Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Shares repurchased (in shares)		2,519,130	1,908,605	2,992,932	3,299,049	4,163,190	2,787,936				13,243,107
Repurchases of common stock		$ 111	$ 79	$ 120	$ 130	$ 152	$ 98				$ 500
Average price paid per share (in dollars per share)		$ 43.89	$ 41.62	$ 40.09	$ 39.41	$ 36.48	$ 35.20				$ 37.76
Repurchase authorized amount													$ 300
Subsequent Event [Member] | Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Shares repurchased (in shares)	1,317,094									5,744,829		100,300,786
Repurchases of common stock	$ 58									$ 248		$ 2,964
Average price paid per share (in dollars per share)	$ 43.59									$ 43.07		$ 29.55
Repurchase authorized amount	$ 300									$ 300		$ 300
Remaining capacity of shares repurchase program	$ 450									$ 450		$ 450