Long-Term Debt and Shareholders' Equity (Shareholders' Equity Narrative) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Shares outstanding (in shares)		156.5
Common stock, par value (in dollars per share)		$ 0.001	$ 0.001
Common stock and additional paid-in capital		$ 2,200
Common stock and additional paid-in capital change		$ 441
Common stock and additional paid-in capital percentage change		16.00%
Common stock repurchased (in shares)		8.5
Fair value of stock repurchased		$ 475
Average price per share of stock repurchased (in dollars per share)		$ 55.88
Preferred stock redeemed		$ 126
Accumulated other comprehensive income		$ 64	$ 325
Series H Preferred Stock
Class of Stock [Line Items]
Preferred stock dividend rate	5.75%
Preferred stock redeemed	$ 126