Derivatives and Hedging Activities - Credit Derivatives (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	$ 669,663	$ 690,466
Maximum Payout/Notional Amount of Purchased Credit Derivatives	722,220	733,980
Offsetting Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	569,142	604,212
Other Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	153,081	129,765
Less than 1 Year [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	222,608	223,191
1 - 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	365,083	409,092
Greater than 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	81,972	58,183
Written Credit Derivative [Member]
Derivative [Line Items]
Fair Value Asset of Written Credit Derivatives	15,153	14,757
Fair Value Liability of Written Credit Derivatives	7,557	9,833
Fair Value Net Asset/(Liability) of Written Credit Derivatives	7,596	4,924
0 - 250 [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	619,755	635,912
0 - 250 [Member] | Offsetting Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	531,632	558,305
0 - 250 [Member] | Other Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	138,756	119,509
0 - 250 [Member] | Less than 1 Year [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	207,898	207,727
0 - 250 [Member] | 1 - 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	337,949	375,208
0 - 250 [Member] | Greater than 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	73,908	52,977
0 - 250 [Member] | Written Credit Derivative [Member]
Derivative [Line Items]
Fair Value Asset of Written Credit Derivatives	14,252	13,919
Fair Value Liability of Written Credit Derivatives	1,844	2,436
Fair Value Net Asset/(Liability) of Written Credit Derivatives	12,408	11,483
251 - 500 [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	24,983	27,002
251 - 500 [Member] | Offsetting Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	16,116	20,588
251 - 500 [Member] | Other Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	9,863	7,712
251 - 500 [Member] | Less than 1 Year [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	8,016	5,819
251 - 500 [Member] | 1 - 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	10,995	17,255
251 - 500 [Member] | Greater than 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	5,972	3,928
251 - 500 [Member] | Written Credit Derivative [Member]
Derivative [Line Items]
Fair Value Asset of Written Credit Derivatives	650	606
Fair Value Liability of Written Credit Derivatives	538	902
Fair Value Net Asset/(Liability) of Written Credit Derivatives	112	(296)
501 - 1000 [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	11,904	10,704
501 - 1000 [Member] | Offsetting Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	10,521	10,133
501 - 1000 [Member] | Other Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	2,082	1,098
501 - 1000 [Member] | Less than 1 Year [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	1,629	1,016
501 - 1000 [Member] | 1 - 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	8,711	8,643
501 - 1000 [Member] | Greater than 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	1,564	1,045
501 - 1000 [Member] | Written Credit Derivative [Member]
Derivative [Line Items]
Fair Value Asset of Written Credit Derivatives	192	187
Fair Value Liability of Written Credit Derivatives	904	809
Fair Value Net Asset/(Liability) of Written Credit Derivatives	(712)	(622)
Greater than 1000 [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	13,021	16,848
Greater than 1000 [Member] | Offsetting Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	10,873	15,186
Greater than 1000 [Member] | Other Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	2,380	1,446
Greater than 1000 [Member] | Less than 1 Year [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	5,065	8,629
Greater than 1000 [Member] | 1 - 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	7,428	7,986
Greater than 1000 [Member] | Greater than 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	528	233
Greater than 1000 [Member] | Written Credit Derivative [Member]
Derivative [Line Items]
Fair Value Asset of Written Credit Derivatives	59	45
Fair Value Liability of Written Credit Derivatives	4,271	5,686
Fair Value Net Asset/(Liability) of Written Credit Derivatives	$ (4,212)	$ (5,641)