Income Taxes Accounting for Uncertainty in Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits, Beginning Balance	$ 33	$ 34	$ 34
Addition based on tax positions related to the current year	1	2
Increase for tax positions of prior years	6		6
Decrease for tax positions of prior years	(2)
Decrease for statute of limitation expiration	(3)	(3)	(6)
Unrecognized Tax Benefits, Ending Balance	$ 35	$ 33	$ 34