Employee Benefit Plans (Summary of Changes in the Corporation's Qualified Defined Benefit Pension Plan's Level 3 Investments Measured at Fair Value on a Recurring Basis) (Details) - Private placements - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Balance at beginning of period	$ 58	$ 57
Net Gains (Losses) Realized	2	1
Net Gains (Losses) Unrealized	(4)	3
Purchases	44	57
Sales	(50)	(60)
Balance at end of period	$ 50	$ 58

Employee Benefit Plans (Summary of Changes in the Corporation's Qualified Defined Benefit Pension Plan's Level 3 Investments Measured at Fair Value on a Recurring Basis) (Details) - Private placements - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2021

Dec. 31, 2020

Balance at beginning of period

$ 58

$ 57

Net Gains (Losses) Realized

Net Gains (Losses) Unrealized

(4)

Purchases

Sales

(50)

(60)

Balance at end of period

$ 50

$ 58