Accumulated Other Comprehensive Income - Changes in AOCI (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (356)	$ (352)
Other comprehensive income before reclassification, net of income taxes	87	36
Amounts reclassified from accumulated other comprehensive income, net of income taxes (a)	(10)	(8)
Net current-period other comprehensive income, net of income taxes	77	28
Ending balance	(279)	(324)
Unrealized Gains (Losses) on Securities Available for Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(4)	(63)
Other comprehensive income before reclassification, net of income taxes	55	29
Net current-period other comprehensive income, net of income taxes	55	29
Ending balance	51	(34)
Unrealized Gains (Losses) on Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(8)	(11)
Other comprehensive income before reclassification, net of income taxes	45	7
Amounts reclassified from accumulated other comprehensive income, net of income taxes (a)	(13)	(8)
Net current-period other comprehensive income, net of income taxes	32	(1)
Ending balance	24	(12)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	22	42
Other comprehensive income before reclassification, net of income taxes	(13)
Amounts reclassified from accumulated other comprehensive income, net of income taxes (a)		(2)
Net current-period other comprehensive income, net of income taxes	(13)	(2)
Ending balance	9	40
Net Pension and Postretirement Benefit Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(366)	(320)
Amounts reclassified from accumulated other comprehensive income, net of income taxes (a)	3	2
Net current-period other comprehensive income, net of income taxes	3	2
Ending balance	$ (363)	$ (318)