Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified				3 Months Ended
	Mar. 31, 2014 Minimum [Member]	Mar. 31, 2014 Maximum [Member]	Aug. 19, 2011 United Guaranty [Member]	Mar. 31, 2014 Cash payment for litigation [Member] Potential Mortgage Servicing Settlement and Claims [Member]	Mar. 31, 2014 Civil money penalty [Member] Consent Order Foreclosure Actions [Member]	Mar. 31, 2014 Consumer relief obligation [Member] Potential Mortgage Servicing Settlement and Claims [Member]
Aggregate range of reasonably possible losses on legal matters in excess of the accrued liability	$ 0	$ 350
Loss Contingency, Damages Awarded, Value				468	160	500
Contingent Receipt, Judgement Award for Damages			34
Contingent Receipt, Judgement Interest Award			6
Contingent Receipt, Judgement Award for Claims Fees			5
Contingent Receipt, Total Judgment Award			$ 45