Activity of the Components of Other Comprehensive Income and Accumulated Other Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net activity for accumulated net unrealized gain (loss) on available-for-sale securities
Unrealized holding gains (losses) on available-for-sale securities arising during period	$ 69	$ 22	$ (178)	$ 19
Reclassification adjustment for net gains included in net income	(4)	(4)	34	(10)
Net activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding (losses) gains on cash flow hedge derivatives arising during period	6	8	5	23
Reclassification adjustment for net (gains) losses on cash flow hedge derivatives included in net income	(4)	(14)	(24)	(41)
Net activity for defined benefit plans, net
Net actuarial loss	2	2	6	7
Total Other Comprehensive Activity
Pre-tax activity total	107	18	(241)	(4)
Total, Tax	(38)	(4)	84	2
Other comprehensive income (loss), Net of Tax	69	14	(157)	(2)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	149	454	375	470
Other comprehensive income (loss), Net of Tax	69	14	(157)	(2)
Total Accumulated Other Comprehensive Income - Ending Balance	218	468	218	468
Accumulated Net Unrealized Investment Gain (Loss)
Pre-tax activity for accumulated net unrealized gain (loss) on available-for-sale securities
Unrealized holding gains on available-for-sale securities arising during period	106	33	(274)	29
Reclassification adjustment for net losses (gains) included in net income	(5)	(6)	53	(16)
Net unrealized gains on available-for-sale securities	101	27	(221)	13
Tax effect for accumulated net unrealized gain (loss) on available-for-sale securities
Unrealized holding losses on available-for-sale securities arising during period	(37)	(11)	96	(10)
Reclassification adjustment for net losses (gains) included in net income	1	2	(19)	6
Net unrealized gains on available-for-sale securities	(36)	(9)	77	(4)
Net activity for accumulated net unrealized gain (loss) on available-for-sale securities
Unrealized holding gains (losses) on available-for-sale securities arising during period	69	22	(178)	19
Reclassification adjustment for net gains included in net income	(4)	(4)	34	(10)
Net unrealized gains on available-for-sale securities	65	18	(144)	9
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	65	18	(144)	9
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	203	476	412	485
Other comprehensive income (loss), Net of Tax	65	18	(144)	9
Total Accumulated Other Comprehensive Income - Ending Balance	268	494	268	494
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Pre-tax activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains on cash flow hedge derivatives arising during period	9	10	8	35
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(6)	(22)	(37)	(63)
Net unrealized gains on cash flow hedge derivatives	3	(12)	(29)	(28)
Tax effect for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	(3)	(2)	(3)	(12)
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	2	8	13	22
Net unrealized gains on cash flow hedge derivatives	(1)	6	10	10
Net activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding (losses) gains on cash flow hedge derivatives arising during period	6	8	5	23
Reclassification adjustment for net (gains) losses on cash flow hedge derivatives included in net income	(4)	(14)	(24)	(41)
Net unrealized gains on cash flow hedge derivatives	2	(6)	(19)	(18)
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	2	(6)	(19)	(18)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	29	(68)	50	80
Other comprehensive income (loss), Net of Tax	2	(6)	(19)	(18)
Total Accumulated Other Comprehensive Income - Ending Balance	31	(62)	31	(62)
Accumulated Defined Benefit Plans Adjustment
Pre-tax activity for defined benefit plans, net
Net actuarial loss	3	3	9	11
Defined benefit plans, net	3	3	9	11
Tax effect for defined benefit plans, net
Net actuarial loss	(1)	(1)	(3)	(4)
Defined benefit plans, net	1	1	3	4
Net activity for defined benefit plans, net
Net actuarial loss	2	2	6	7
Defined benefit plans, net	(2)	(2)	(6)	(7)
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	2	2	6	7
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	(83)	(90)	(87)	(95)
Other comprehensive income (loss), Net of Tax	2	2	6	7
Total Accumulated Other Comprehensive Income - Ending Balance	$ (81)	$ (88)	$ (81)	$ (88)