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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 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	$ (69)	$ 69	$ 233	$ (178)
Reclassification adjustment for net (gains) losses included in net income	(3)	(4)	(16)	34
Net activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	(3)	6	19	5
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(7)	(4)	(20)	(24)
Net activity for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs	(1)	(2)	(3)	(6)
Total Other Comprehensive Activity
Pre-tax activity total	(122)	107	336	(241)
Total, Tax	41	(38)	(117)	84
Other comprehensive income (loss), Net of Tax	(81)	69	219	(157)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	382	149	82	375
Other comprehensive income (loss), Net of Tax	(81)	69	219	(157)
Total Accumulated Other Comprehensive Income - Ending Balance	301	218	301	218
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	(105)	106	357	(274)
Reclassification adjustment for net losses (gains) included in net income	(5)	(5)	(25)	53
Net unrealized gains on available-for-sale securities	(110)	101	332	(221)
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	36	(37)	(124)	96
Reclassification adjustment for net losses (gains) included in net income	2	1	9	(19)
Net unrealized gains on available-for-sale securities	38	(36)	(115)	77
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)	69	233	(178)
Reclassification adjustment for net (gains) losses included in net income	(3)	(4)	(16)	34
Net unrealized gains on available-for-sale securities	(72)	65	217	(144)
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	(72)	65	217	(144)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	410	203	121	412
Other comprehensive income (loss), Net of Tax	(72)	65	217	(144)
Total Accumulated Other Comprehensive Income - Ending Balance	338	268	338	268
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	(4)	9	30	8
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(10)	(6)	(31)	(37)
Net unrealized gains on cash flow hedge derivatives	(14)	3	(1)	(29)
Tax effect for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	1	(3)	(11)	(3)
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	3	2	11	13
Net unrealized gains on cash flow hedge derivatives	4	(1)		10
Net activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	(3)	6	19	5
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(7)	(4)	(20)	(24)
Net unrealized gains on cash flow hedge derivatives	(10)	2	(1)	(19)
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	(10)	2	(1)	(19)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	22	29	13	50
Other comprehensive income (loss), Net of Tax	(10)	2	(1)	(19)
Total Accumulated Other Comprehensive Income - Ending Balance	12	31	12	31
Accumulated Defined Benefit Plans Adjustment
Pre-tax activity for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs	2	3	5	9
Defined benefit plans, net	2	3	5	9
Tax effect for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs	(1)	(1)	(2)	(3)
Defined benefit plans, net	(1)	(1)	(2)	(3)
Net activity for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs	1	2	3	6
Defined benefit plans, net	1	2	3	6
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	(1)	(2)	(3)	(6)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	(50)	(83)	(52)	(87)
Other comprehensive income (loss), Net of Tax	(1)	(2)	(3)	(6)
Total Accumulated Other Comprehensive Income - Ending Balance	$ (49)	$ (81)	$ (49)	$ (81)