Derivatives and Hedging Activities - Credit Derivatives Sold and Held (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Credit Derivatives [Line Items]
Notional Amount	$ 22	$ 15
Average Term (Years)	0 years	0 years
Payment / Performance Risk	0.00%	0.00%
Other [Member]
Credit Derivatives [Line Items]
Notional Amount	$ 22	$ 15
Average Term (Years)	13 years 5 months 4 days	3 years 29 days
Payment / Performance Risk	17.18%	6.64%