Litigation and Regulatory Matters - Additional Information (Detail) (USD $)	12 Months Ended	1 Months Ended		9 Months Ended				0 Months Ended		1 Months Ended			0 Months Ended		1 Months Ended		1 Months Ended		1 Months Ended	93 Months Ended	11 Months Ended	1 Months Ended		9 Months Ended	1 Months Ended	3 Months Ended		12 Months Ended		12 Months Ended
	Feb. 28, 2013 servicers	Nov. 30, 2012 Esslinger [Member] appeal	Oct. 31, 2012 DeKalb County vs. HSBC North America Holdings [Member] county	Sep. 30, 2013 Obligations to Repurchase Mortage Loans [Member]	Sep. 30, 2013 Obligations to Repurchase Real Estate Secured Receivables [Member]	Sep. 30, 2013 Minimum [Member] Obligations to Repurchase Mortage Loans [Member]	Sep. 30, 2013 Maximum [Member] Obligations to Repurchase Mortage Loans [Member]	Oct. 17, 2013 Securities Litigation [Member]	Jul. 30, 2013 Securities Litigation [Member]	Sep. 30, 2012 Securities Litigation [Member]	Dec. 31, 2011 Securities Litigation [Member] claim	Aug. 31, 2002 Securities Litigation [Member] state	Oct. 17, 2013 Securities Litigation [Member] Subsequent Event [Member]	Sep. 30, 2013 Securities Litigation [Member] Subsequent Event [Member]	Sep. 30, 2012 Securities Litigation [Member] Minimum [Member]	Mar. 31, 2010 Securities Litigation [Member] Minimum [Member]	Sep. 30, 2012 Securities Litigation [Member] Maximum [Member]	Mar. 31, 2010 Securities Litigation [Member] Maximum [Member]	Sep. 30, 2012 Pending Supplemental Notices [Member]	Mar. 31, 2013 Cards Litigation [Member] class_action	May 31, 2011 Debt Cancellation Litigation [Member] class_action	Apr. 30, 2012 Debt Cancellation Litigation [Member] Hawaii Attorney General [Member] company	Jan. 31, 2013 Telephone Consumer Protection Act Litigation [Member] claim	Sep. 30, 2013 Telephone Consumer Protection Act Litigation [Member] TCPA [Member]	Feb. 29, 2012 Foreclosure Litigation [Member] servicer	Jun. 30, 2013 Foreclosure Litigation [Member]	Dec. 31, 2011 Foreclosure Litigation [Member]	Dec. 31, 2012 Foreclosure Litigation [Member]	Feb. 28, 2013 Foreclosure Litigation [Member] state	Feb. 28, 2013 Foreclosure Litigation [Member] HSBC North America [Member]	Dec. 31, 2012 Foreclosure Litigation [Member] HSBC North America [Member]
Loss Contingencies [Line Items]
Number of states in settlement												46
Estimated damage																$ 2,400,000,000		$ 3,200,000,000
Total claims of loss											45,921
Aggregate amount of claims				970,000,000							2,200,000,000								179,000,000
Portion of reasonable possible loss not accrued for					5,500,000,000	0	148,000,000
Litigation judgment claims								2,500,000,000	1,500,000,000				2,500,000,000		1,500,000,000		2,200,000,000
Claims still open to special court								527,000,000		510,000,000
Possible future expenses related to amount of damages														3,500,000,000
Class actions filed																				4	8
Number of appeals dismissed		2
Number of appeals filed		3
Number of appeals voluntarily dismissed		1
Number of credit card companies have lawsuits	12																					7
Number of counties filing lawsuit			3
Number of claims																							2
Statutory damages for each violation (usd per violation)																								500
Statutory damages for each willful violation (usd per violation)																								1,500
Cash payments mortgage servicers would pay in excess	9,300,000,000
Cash payment into a fund hat will be used to make payments to borrowers																														96,000,000
Recorded expenses in period																												85,000,000			104,000,000
Number of states in settlement with U.S. mortgage servicers																													49
Number of U.S. mortgage servicers																									5
Accrual																											157,000,000
Decrease in accrual																										$ (14,000,000)