Fair Values of Assets and Liabilities - Losses Recognized Related to Nonrecurring Fair Value Measurements of Individual Assets or Portfolios (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Loans	$ 22	$ 12	$ 55	$ 51
Other assets	$ 14	$ 42	$ 73	$ 129