Derivatives (Cash Flow Hedges) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	$ 6	$ (8)	$ 5	$ 19
Maximum Length of Time Hedged in Cash Flow Hedge			8 years		8 years
Accumulated Other Comprehensive Income Loss	$ 2,000		$ 2,000		$ 1,900