Income Taxes - Total Income Tax (Benefit) Expense and Resulting Effective Tax Rate (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Line Items]
Income (loss) before income taxes times 35% statutory federal tax rate	$ 384	$ 471	$ 278
Amortization of tax-advantaged investments	64	65	59
Foreign tax adjustments	1	17	24
Reduced tax rate on lease financing income	(51)		6
Tax-exempt interest income	(16)	(16)	(17)
Corporate-owned life insurance income	(43)	(42)	(48)
Increase (decrease) in tax reserves		2	(6)
Interest refund (net of federal tax benefit)		(24)
State income tax, net of federal tax benefit	9	(1)	5
Tax credits	(119)	(125)	(117)
Other	10	22	2
Income tax (benefit) expense	$ 239	$ 369	$ 186
Federal income tax rate	35.00%	35.00%	35.00%
Amortization of tax-advantaged investments	5.90%	4.80%	7.40%
Foreign tax adjustments,rate	0.10%	1.30%	3.00%
Reduced tax rate on lease financing income, rate	(4.60%)		0.80%
Tax-exempt interest income, rate	(1.50%)	(1.20%)	(2.10%)
Corporate-owned life insurance income, rate	(3.90%)	(3.10%)	(6.00%)
Increase (decrease) in tax reserves,rate		0.10%	(0.80%)
Interest refund (net of federal tax benefit),rate		(1.80%)
State income tax, net of federal tax benefit,rate	0.80%		0.60%
Tax credits,rate	(10.90%)	(9.30%)	(14.70%)
Other,rate	0.90%	1.60%	0.20%
Total income tax expense (benefit),rate	21.80%	27.40%	23.40%