Long-Term Debt and Shareholders' Equity (Shareholders' Equity Narrative) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Shares outstanding (in shares)	162.2	162.2
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001
Common stock and additional paid-in capital	$ 2,600	$ 2,600
Common stock and additional paid-in capital change	$ 121	$ 121
Common stock and additional paid-in capital percentage change	5.00%	5.00%
Common stock repurchased (in shares)		2.7
Fair value of stock repurchased		$ 150
Average price per share of stock repurchased (in dollars per share)		$ 54.94
Preferred stock redeemed	$ 126	$ 126
Accumulated other comprehensive income	$ 175	$ 175	$ 325
Series H Preferred Stock
Class of Stock [Line Items]
Preferred stock dividend rate	5.75%
Preferred stock redeemed	$ 126