Derivatives and Hedging Activities - Credit Derivatives (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	$ 798,194	$ 923,477
Maximum Payout/Notional Amount of Purchased Credit Derivatives	840,180	968,680
Offsetting Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	692,043	821,571
Other Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	148,139	147,110
Less than 1 Year [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	244,751	256,741
1 - 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	449,040	599,983
Greater than 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	104,403	66,753
Written Credit Derivative [Member]
Derivative [Line Items]
Fair Value Asset of Written Credit Derivatives	16,693	18,332
Fair Value Liability of Written Credit Derivatives	11,660	19,779
Fair Value Net Asset/(Liability) of Written Credit Derivatives	5,033	(1,447)
0 - 250 [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	726,295	812,508
0 - 250 [Member] | Offsetting Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	631,589	722,436
0 - 250 [Member] | Other Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	134,755	132,757
0 - 250 [Member] | Less than 1 Year [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	228,332	240,468
0 - 250 [Member] | 1 - 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	407,671	514,986
0 - 250 [Member] | Greater than 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	90,292	57,054
0 - 250 [Member] | Written Credit Derivative [Member]
Derivative [Line Items]
Fair Value Asset of Written Credit Derivatives	15,280	17,110
Fair Value Liability of Written Credit Derivatives	2,978	2,756
Fair Value Net Asset/(Liability) of Written Credit Derivatives	12,302	14,354
251 - 500 [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	34,929	51,739
251 - 500 [Member] | Offsetting Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	26,543	46,313
251 - 500 [Member] | Other Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	9,281	6,383
251 - 500 [Member] | Less than 1 Year [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	6,064	2,859
251 - 500 [Member] | 1 - 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	19,029	42,399
251 - 500 [Member] | Greater than 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	9,836	6,481
251 - 500 [Member] | Written Credit Derivative [Member]
Derivative [Line Items]
Fair Value Asset of Written Credit Derivatives	947	924
Fair Value Liability of Written Credit Derivatives	1,037	2,596
Fair Value Net Asset/(Liability) of Written Credit Derivatives	(90)	(1,672)
501 - 1000 [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	15,035	20,775
501 - 1000 [Member] | Offsetting Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	14,590	19,556
501 - 1000 [Member] | Other Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	1,635	3,372
501 - 1000 [Member] | Less than 1 Year [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	2,188	2,881
501 - 1000 [Member] | 1 - 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	10,016	16,327
501 - 1000 [Member] | Greater than 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	2,831	1,567
501 - 1000 [Member] | Written Credit Derivative [Member]
Derivative [Line Items]
Fair Value Asset of Written Credit Derivatives	269	108
Fair Value Liability of Written Credit Derivatives	1,048	1,942
Fair Value Net Asset/(Liability) of Written Credit Derivatives	(779)	(1,834)
Greater than 1000 [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	21,935	38,455
Greater than 1000 [Member] | Offsetting Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	19,321	33,266
Greater than 1000 [Member] | Other Purchased Credit Derivatives [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Purchased Credit Derivatives	2,468	4,598
Greater than 1000 [Member] | Less than 1 Year [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	8,167	10,533
Greater than 1000 [Member] | 1 - 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	12,324	26,271
Greater than 1000 [Member] | Greater than 5 Years [Member]
Derivative [Line Items]
Maximum Payout/Notional Amount of Written Credit Derivative	1,444	1,651
Greater than 1000 [Member] | Written Credit Derivative [Member]
Derivative [Line Items]
Fair Value Asset of Written Credit Derivatives	197	190
Fair Value Liability of Written Credit Derivatives	6,597	12,485
Fair Value Net Asset/(Liability) of Written Credit Derivatives	$ (6,400)	$ (12,295)