Litigation and Regulatory Matters - Additional Information (Detail) mortgage_loan in Thousands		1 Months Ended											3 Months Ended	12 Months Ended
	Apr. 13, 2016 USD ($)	Jun. 30, 2016 USD ($)	Apr. 30, 2016 USD ($)	Feb. 29, 2016 USD ($)	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	Jun. 30, 2014 USD ($)	Dec. 31, 2016 USD ($) bank lawsuit	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														$ 390,000,000
Number of mortgage loans that suffered alleged loss | mortgage_loan						16
Number of similar cases pending review by U.S. Supreme Court | lawsuit														2
Obligations to Repurchase Mortgage Loans [Member]
Loss Contingencies [Line Items]
Aggregate amount of claims														$ 500,000,000
Number of Banks Sued by the Department of Justice | bank														1
Number of banks that have reported settlements | bank														8
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
Benchmark Rate Litigation [Member]
Loss Contingencies [Line Items]
Total claims of loss | plaintiff					2
Securities Litigation [Member]
Loss Contingencies [Line Items]
Litigation settlement amount		$ 1,575,000,000
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]
Aggregate amount of claims			$ 500
Credit Monitoring Product [Member]
Loss Contingencies [Line Items]
Civil penalty assessed	$ 35,000,000
Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Number of servicers subject to new servicing framework | 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)
HSBC North America [Member] | Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Cash payments into fund									$ 96,000,000
Federal and State Parties [Member] | Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Litigation settlement amount				$ 100,000,000
Consumer Relief through Receivable Modification Programs [Member] | Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Litigation settlement amount				370,000,000
Federal Reserve [Member] | Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Civil penalty assessed				131,000,000
Affiliated Entities [Member] | Foreclosure Litigation [Member]
Loss Contingencies [Line Items]
Litigation settlement amount				$ 32,000,000