Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	May 22, 2020	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Preferred stock, authorized shares (in shares)		4,400,000	4,400,000
Liquidation preference of preferred stock (per share)		$ 1,000
Preferred stock, liquidation preference per depositary share (in dollars per share)		$ 25
Depositary share, preferred stock ownership interest		0.025%
Shares outstanding (in shares)		164,100,000
Common stock, par value (in dollars per share)		$ 0.001	$ 0.001
Common stock and additional paid-in capital		$ 2,700
Common stock and additional paid-in capital decrease		$ 49
Common stock and additional paid-in capital decrease (as a percent)		2.00%
Common stock repurchased (in shares)		1,700,000	23,500,000
Fair value of stock repurchased		$ 75	$ 1,100
Average price per share of stock repurchased (in dollars per share)		$ 45.02	$ 46.80
Accumulated other comprehensive income		$ 325	$ 43
Common stock held in trust		13	13
Total invested assets of trusts		120	113
Total obligations of trusts		$ 133	$ 126
Warrant
Schedule of Equity Method Investments [Line Items]
Warrants expired unexercised (in shares)	29,200,000
Warrant exercise price (in dollars per share)	$ 33.31
Common stock, conversion (in shares)	1.10