Derivative Instruments - Additional Information (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Dec. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Realized and unrealized losses on derivatives classified as cash flow hedges recorded in other comprehensive income (loss)			$ 125,000,000	$ 172,000,000
Forward commitments to sell mortgage loans			9,600,000,000
Hedged mortgage loans held for sale			4,500,000,000
Unfunded mortgage loan commitments			6,400,000,000
Non-derivative debt instruments designated as net investment hedges			0	$ 0
Fair value of derivatives under collateral agreements in a net liability position			915,000,000
Collateral posted by company netted against net liability position			$ 759,000,000
Scenario, Forecast [Member]
Derivative [Line Items]
Estimated loss to be reclassified from other comprehensive income (loss) into earnings	$ 56,000,000	$ 94,000,000