Activity of the Components of Other Comprehensive Income and Accumulated Other Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
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	$ 188	$ (211)	$ 301	$ (247)
Reclassification adjustment for net (gains) losses included in net income	(9)	33	(12)	38
Net activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	12	(2)	22	(1)
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(6)	(6)	(13)	(20)
Net activity for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs	(1)	(2)	(2)	(4)
Total Other Comprehensive Activity
Pre-tax activity total	283	(282)	458	(348)
Total, Tax	(97)	98	(158)	122
Other comprehensive income (loss), Net of Tax	186	(184)	300	(226)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	196	333	82	375
Other comprehensive income (loss), Net of Tax	(186)	184	(300)	226
Total Accumulated Other Comprehensive Income - Ending Balance	382	149	382	149
Accumulated Net Unrealized Investment Gain (Loss)
Pre-tax activity for accumulated net unrealized gain (loss) on available-for-sale securities
Unrealized holding gains (losses) on available-for-sale securities arising during period	288	(324)	461	(380)
Reclassification adjustment for net losses (gains) included in net income	(14)	51	(19)	58
Net unrealized gains on available-for-sale securities	274	(273)	442	(322)
Tax effect for accumulated net unrealized gain (loss) on available-for-sale securities
Unrealized holding gains (losses) on available-for-sale securities arising during period	(100)	113	(160)	133
Reclassification adjustment for net losses (gains) included in net income	5	(18)	7	(20)
Net unrealized gains on available-for-sale securities	(95)	95	(153)	113
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	188	(211)	301	(247)
Reclassification adjustment for net (gains) losses included in net income	(9)	33	(12)	38
Net unrealized gains on available-for-sale securities	179	(178)	289	(209)
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	179	(178)	289	(209)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	231	381	121	412
Other comprehensive income (loss), Net of Tax	(179)	178	(289)	209
Total Accumulated Other Comprehensive Income - Ending Balance	410	203	410	203
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 (losses) on cash flow hedge derivatives arising during period	19	(2)	34	(1)
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(11)	(10)	(21)	(31)
Net unrealized gains on cash flow hedge derivatives	8	(12)	13	(32)
Tax effect for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	(7)		(12)
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	5	4	8	11
Net unrealized gains on cash flow hedge derivatives	(2)	4	(4)	11
Net activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	12	(2)	22	(1)
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(6)	(6)	(13)	(20)
Net unrealized gains on cash flow hedge derivatives	6	(8)	9	(21)
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	6	(8)	9	(21)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	16	37	13	50
Other comprehensive income (loss), Net of Tax	(6)	8	(9)	21
Total Accumulated Other Comprehensive Income - Ending Balance	22	29	22	29
Accumulated Defined Benefit Plans Adjustment
Pre-tax activity for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs	1	3	3	6
Defined benefit plans, net	1	3	3	6
Tax effect for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs		(1)	(1)	(2)
Defined benefit plans, net		(1)	(1)	(2)
Net activity for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs	1	2	2	4
Defined benefit plans, net	1	2	2	4
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	(1)	(2)	(2)	(4)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	(51)	(85)	(52)	(87)
Other comprehensive income (loss), Net of Tax	1	2	2	4
Total Accumulated Other Comprehensive Income - Ending Balance	$ (50)	$ (83)	$ (50)	$ (83)