Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified			9 Months Ended		9 Months Ended
	Sep. 30, 2014 Minimum [Member]	Sep. 30, 2014 Maximum [Member]	Sep. 30, 2014 Mortgage Modification Investigation and HAMP [Member]	Aug. 19, 2011 United Guaranty [Member]	Sep. 30, 2014 Consumer Remediation [Member] Mortgage Modification Investigation and HAMP [Member]	Sep. 30, 2014 Consumer Remediation [Member] Mortgage Modification Investigation and HAMP [Member] Maximum [Member]	Sep. 30, 2014 Cash payment for litigation [Member] Potential Mortgage Servicing Settlement and Claims [Member]	Sep. 30, 2014 Housing counseling for homeowners [Member] Mortgage Modification Investigation and HAMP [Member]	Sep. 30, 2014 Civil money penalty [Member] Consent Order Foreclosure Actions [Member]	Sep. 30, 2014 Consumer relief obligation [Member] Potential Mortgage Servicing Settlement and Claims [Member]	Sep. 30, 2014 Total Cash Payment for Settlement [Domain] Mortgage Modification Investigation and HAMP [Member]	Sep. 30, 2014 Mortgage Modification Investigation and HAMP [Member] Restitution to Fannie Mae and Freddie Mac [Member]	Sep. 30, 2014 Mortgage Modification Investigation and HAMP [Member] Cash payment for litigation [Member]
Aggregate range of reasonably possible losses on legal matters in excess of the accrued liability	$ 0	$ 300
Loss Contingency, Damages Awarded, Value			204		179	274	468	20	160	500	46	10	16
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