Stock-based Compensation (Summary of Restricted Stock Awards Vested) (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement, Noncash Expense [Abstract]
Total shares vested	1.0	1.0	1.0
Fair value on vesting date	$ 199	$ 220	$ 135

Aggregate value of stock related to Restricted Stock Awards issued during the period.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration