Litigation and Regulatory Matters - Additional Information (Detail) mortgage_loan in Thousands				1 Months Ended									9 Months Ended	12 Months Ended
	Feb. 17, 2016 USD ($)	Mar. 17, 2015 USD ($)	Oct. 17, 2013 USD ($)	Feb. 22, 2016 USD ($) entity	May. 31, 2014 plaintiff	Dec. 31, 2013 mortgage_loan	Nov. 30, 2013 USD ($)	Oct. 31, 2013 USD ($)	Feb. 28, 2013 USD ($) servicer	Oct. 31, 2012 county	Feb. 29, 2012 state servicer	Dec. 31, 2011 USD ($) claim	Jan. 31, 2013 class_action	Dec. 31, 2015 USD ($) bank	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Aug. 31, 2002 state
Loss Contingencies [Line Items]
Estimate of possible loss for all litigation matters														$ 3,100,000,000
Litigation judgment claims			$ 2,500,000,000
Benchmark Rate Litigation [Member]
Loss Contingencies [Line Items]
Total claims of loss | plaintiff					2
DeKalb County vs. HSBC North America Holdings [Member]
Loss Contingencies [Line Items]
Number of counties filing lawsuit | county										3
Number of counties constituting metropolitan area of Atlanta, Georgia | county										5
Telephone Consumer Protection Act Litigation [Member]
Loss Contingencies [Line Items]
Total claims of loss | class_action													2
Litigation settlement amount		$ 40,000,000
Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Number of other credit card servicers involved in settlement | servicer									12
Cash payments and other assistance to eligible borrowers (in excess)									$ 9,300,000,000
Recorded expenses in period																	$ 85,000,000
Number of states In settlement with U.S. mortgage servicers | state											49
Number of U.S. mortgage servicers | servicer											5
Accrual																		$ 157,000,000
Increase (decrease) in reserve															$ (60,000,000)	$ (14,000,000)
Securities Litigation [Member]
Loss Contingencies [Line Items]
Number of states in settlement | state																			46
Total claims of loss | claim												45,921
Aggregate amount of claims												$ 2,200,000,000
Litigation judgment claims							$ 2,500,000,000	$ 2,500,000,000
Amount of claims still subject to objections														625,000,000
Legal Fees [Member]
Loss Contingencies [Line Items]
Increase (decrease) in reserve														760,000,000
Obligations to Repurchase Mortage Loans [Member]
Loss Contingencies [Line Items]
Aggregate amount of claims														$ 500,000,000
Number of banks that have reported settlements | bank														5
Number of mortgage loans that suffered alleged losses | mortgage_loan						16
HSBC North America [Member] | Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Cash payments into fund									$ 96,000,000
Recorded expenses in period																	$ 104,000,000
Subsequent Event [Member] | Lender-Placed Insurance Matters [Member]
Loss Contingencies [Line Items]
Litigation settlement amount	$ 4,075,000
Subsequent Event [Member] | Lehman Brothers Holdings Inc. Adversary Proceeding [Member]
Loss Contingencies [Line Items]
Number of entities included in proceeding (nearly) | entity				150
Federal and State Parties [Member] | Subsequent Event [Member] | Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Litigation settlement amount				$ 100,000,000
Consumer Relief through Receivable Modification Programs [Member] | Subsequent Event [Member] | Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Litigation settlement amount				370,000,000
Allocable to the Other Four Largest U.S. Mortgage Servicers [Member] | Subsequent Event [Member] | Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Litigation settlement amount				32,000,000
Federal Reserve [Member] | Subsequent Event [Member] | Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Loss Contingency, Civil Penalty Assessed				$ 131,000,000