Activity of the Components of Other Comprehensive Income and Accumulated Other Comprehensive Income (Detail) (USD $) In Millions	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized holding gains on available-for-sale securities arising during period	$ 135	$ 355
Reclassification adjustment for net gains included in net income	(17)	(23)
Net unrealized gains on available-for-sale securities	118	332
Unrealized holding gains on cash flow hedge derivatives arising during period	32	(2)
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(31)	(29)
Net unrealized gains on cash flow hedge derivatives	1	(31)
Net prior service cost
Net actuarial loss	6	6
Defined benefit plans, net	6	6
Total	125	307
Unrealized holding gains on available-for-sale securities arising during period	(47)	(125)
Reclassification adjustment for net gains included in net income	6	8
Net unrealized gains on available-for-sale securities	(41)	(117)
Unrealized holding gains on cash flow hedge derivatives arising during period	(11)	1
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	11	10
Net unrealized gains on cash flow hedge derivatives		11
Net prior service cost
Net actuarial loss	(2)	(2)
Defined benefit plans, net	(2)	(2)
Total	(43)	(108)
Total Accumulated Other Comprehensive Income - Beginning Balance	314	241
Unrealized holding gains on available-for-sale securities arising during period	88	230
Reclassification adjustment for net gains included in net income	(11)	(15)
Net unrealized gains on available-for-sale securities	77	215
Unrealized holding gains on cash flow hedge derivatives arising during period	21	(1)
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(20)	(19)
Net unrealized gains on cash flow hedge derivatives	1	(20)
Net prior service cost
Net actuarial loss	4	4
Defined benefit plans, net	4	4
Total	82	199
Total Accumulated Other Comprehensive Income - Ending Balance	396	440
Accumulated Net Unrealized Investment Gain (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income - Beginning Balance	321	216
Total	77	215
Total Accumulated Other Comprehensive Income - Ending Balance	398	431
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
Total	1	(20)
Total Accumulated Other Comprehensive Income - Ending Balance	68	85
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income - Beginning Balance	(74)	(80)
Total	4	4
Total Accumulated Other Comprehensive Income - Ending Balance	$ (70)	$ (76)