Securities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($) security	Dec. 31, 2015 USD ($) security	Dec. 31, 2014 USD ($) security
Schedule of Available-for-sale and Held-to-Maturity Securities [Line Items]
Held-to-maturity Securities, Sold Security, at Carrying Value			$ 76,000,000
Held-to-maturity Securities, Sold Security, Realized Gain (Loss)	$ 0	$ 0	$ (9,000,000)
Held-to-maturity Securities [Member]
Schedule of Available-for-sale and Held-to-Maturity Securities [Line Items]
Asset backed securities with changes to other than temporary impairment estimates related to credit component | security	0	0	2
Increase in credit losses for which an other-than-temporary impairment was previously recognized	$ 0	$ 0
Other assets [Member]
Schedule of Available-for-sale and Held-to-Maturity Securities [Line Items]
Federal Home Loan Bank Stock	338,000,000	323,000,000
Federal Reserve Bank Stock	$ 631,000,000	$ 632,000,000