Derivatives and Hedging Activities - Credit Derivatives Sold and Held (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Credit Derivatives [Line Items]
Notional Amount	$ 4	$ 5
Average Term (Years)	0 years	0 years
Payment / Performance Risk	0.00%	0.00%
Other [Member]
Credit Derivatives [Line Items]
Notional Amount	$ 4	$ 5
Average Term (Years)	6 years 5 months 26 days	2 years 8 months 1 day
Payment / Performance Risk	17.93%	14.46%