Activity of the Components of Other Comprehensive Income and Accumulated Other Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 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	$ 113	$ (36)
Reclassification adjustment for net gains included in net income	(3)	5
Net activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains on cash flow hedge derivatives arising during period	10	1
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(7)	(14)
Net activity for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs	1	2
Total Other Comprehensive Activity
Pre-tax activity total	175	(66)
Total, Tax	(61)	24
Other comprehensive income (loss), Net of Tax	114	(42)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	82	375
Other comprehensive income (loss), Net of Tax	114	(42)
Total Accumulated Other Comprehensive Income - Ending Balance	196	333
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	173	(56)
Reclassification adjustment for net losses (gains) included in net income	(5)	7
Net unrealized gains on available-for-sale securities	168	(49)
Tax effect for accumulated net unrealized gain (loss) on available-for-sale securities
Unrealized holding losses on available-for-sale securities arising during period	(60)	20
Reclassification adjustment for net losses (gains) included in net income	2	(2)
Net unrealized gains on available-for-sale securities	(58)	18
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	113	(36)
Reclassification adjustment for net gains included in net income	(3)	5
Net unrealized gains on available-for-sale securities	110	(31)
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	110	(31)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	121	412
Other comprehensive income (loss), Net of Tax	110	(31)
Total Accumulated Other Comprehensive Income - Ending Balance	231	381
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	15	1
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(10)	(21)
Net unrealized gains on cash flow hedge derivatives	5	(20)
Tax effect for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	(5)
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	3	7
Net unrealized gains on cash flow hedge derivatives	(2)	7
Net activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains on cash flow hedge derivatives arising during period	10	1
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(7)	(14)
Net unrealized gains on cash flow hedge derivatives	3	(13)
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	3	(13)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	13	50
Other comprehensive income (loss), Net of Tax	3	(13)
Total Accumulated Other Comprehensive Income - Ending Balance	16	37
Accumulated Defined Benefit Plans Adjustment
Pre-tax activity for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs	(2)	(3)
Defined benefit plans, net	2	3
Tax effect for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs	1	1
Defined benefit plans, net	(1)	(1)
Net activity for defined benefit plans, net
Reclassification of amounts to net periodic benefit costs	(1)	(2)
Defined benefit plans, net	1	2
Total Other Comprehensive Activity
Other comprehensive income (loss), Net of Tax	(1)	(2)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	(52)	(87)
Other comprehensive income (loss), Net of Tax	(1)	(2)
Total Accumulated Other Comprehensive Income - Ending Balance	$ (51)	$ (85)