Activity of the Components of Other Comprehensive Income and Accumulated Other Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized holding gains on available-for-sale securities arising during period	$ 309	$ 216	$ 248
Reclassification adjustment for net gains included in net income	(56)	(57)	(57)
Net unrealized gains on available-for-sale securities	253	159	154
Unrealized holding gains on cash flow hedge derivatives arising during period	89	2	75
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(69)	(60)	(49)
Net unrealized gains on cash flow hedge derivatives	20	(58)	26
Net prior service cost		1
Net actuarial loss	(32)	10	39
Defined benefit plans, net	(32)	11	39
Total	241	112	219
Unrealized holding gains on available-for-sale securities arising during period	(108)	(73)	(86)
Reclassification adjustment for net gains included in net income	19	19	20
Net unrealized gains on available-for-sale securities	(89)	(54)	(53)
Unrealized holding gains on cash flow hedge derivatives arising during period	(31)	(1)	(26)
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	24	21	17
Net unrealized gains on cash flow hedge derivatives	(7)	20	(9)
Net prior service cost		(1)
Net actuarial loss	11	(4)	(14)
Defined benefit plans, net	11	(5)	(14)
Total	(85)	(39)	(76)
Total Accumulated Other Comprehensive Income - Beginning Balance	314	241	98
Unrealized holding gains on available-for-sale securities arising during period	201	143	162
Net unrealized gains on available-for-sale securities	164	105	101
Unrealized holding gains on cash flow hedge derivatives arising during period	58	1	49
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(45)	(39)	(32)
Net unrealized gains on cash flow hedge derivatives	13	(38)	17
Net actuarial loss	(21)	6	25
Defined benefit plans, net	(21)	6	25
Total	156	73	143
Total Accumulated Other Comprehensive Income - Ending Balance	470	314	241
Reclassification adjustment related to prior OTTI charges (pre-tax activity)			(37)
Reclassification adjustment related to prior OTTI charges			(13)
Reclassification adjustment related to prior OTTI charges (net activity)			(24)
Reclassification adjustment for net gains included in net income	(37)	(38)	(37)
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income - Beginning Balance	321	216	115
Total	164	105	101
Total Accumulated Other Comprehensive Income - Ending Balance	485	321	216
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income - Beginning Balance	67	105	88
Total	13	(38)	17
Total Accumulated Other Comprehensive Income - Ending Balance	80	67	105
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income - Beginning Balance	(74)	(80)	(105)
Total	(21)	6	25
Total Accumulated Other Comprehensive Income - Ending Balance	$ (95)	$ (74)	$ (80)