Contingent Liabilities and Guarantees - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($)
Commitments Contingencies And Guarantees [Line Items]
Weighted-average remaining term for outstanding commercial mortgage loans in years	7 years 7 months 6 days
Unpaid principal balance outstanding of loans sold	$ 6,700
Potential undiscounted future payments maximum limit	30% of the principal balance of loans outstanding
Default guarantees, value	$ 121
Written Put Options [Member]
Commitments Contingencies And Guarantees [Line Items]
Default guarantees, value	$ 47
Weighted average life of written put options	2 years
Return Guarantee Agreement with LIHTC Investors [Member]
Commitments Contingencies And Guarantees [Line Items]
Compliance period of property	15 years
Default guarantees, value	$ 3
Expiration of guarantees	Extend through 2018
Standby Letters of Credit [Member]
Commitments Contingencies And Guarantees [Line Items]
Remaining weighted-average life of standby letters of credit in years	2 years 10 months 24 days
Remaining actual life letters of credit in years	From less than one year to as many as 11 years.
Default guarantees, value	$ 67
Default Guarantees [Member]
Commitments Contingencies And Guarantees [Line Items]
Default guarantees, value	$ 1
Minimum [Member] | Low [Member]
Commitments Contingencies And Guarantees [Line Items]
Guarantee Obligations	0.00%
Minimum [Member] | Moderate [Member]
Commitments Contingencies And Guarantees [Line Items]
Guarantee Obligations	30.00%
Minimum [Member] | High [Member]
Commitments Contingencies And Guarantees [Line Items]
Guarantee Obligations	70.00%
Maximum [Member] | Low [Member]
Commitments Contingencies And Guarantees [Line Items]
Guarantee Obligations	30.00%
Maximum [Member] | Moderate [Member]
Commitments Contingencies And Guarantees [Line Items]
Guarantee Obligations	70.00%