Commitments, Contingencies and Guarantees - Narrative (Details)	1 Months Ended		3 Months Ended
	Dec. 31, 2017 USD ($)	Jun. 30, 2013 patent	Mar. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Loss contingency accrual			$ 27,000,000
Minimum
Loss Contingencies [Line Items]
Loss contingency accrual			0
Maximum
Loss Contingencies [Line Items]
Loss contingency accrual			76,000,000
Financial Standby Letter of Credit
Loss Contingencies [Line Items]
Letters of credit, deferred fees	$ 9,000,000		8,000,000
Maximum potential amount of future undiscounted payments Company could be required to make on outstanding standby letters of credit			$ 1,400,000,000
Financial Standby Letter of Credit | Minimum
Loss Contingencies [Line Items]
Standby and commercial letters of credit expiration term			1 year
Financial Standby Letter of Credit | Maximum
Loss Contingencies [Line Items]
Standby and commercial letters of credit expiration term			4 years
Potential Recourse Related To FNMA Securitizations | Maximum
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss	19,000,000		$ 19,000,000
Accrued Expenses and Other Liabilities | Financial Standby Letter of Credit
Loss Contingencies [Line Items]
Loss contingency accrual	83,000,000		80,000,000
Accrued Expenses and Other Liabilities | Potential Recourse Related To FNMA Securitizations
Loss Contingencies [Line Items]
Loss contingency accrual			793,000
Accrued Expenses and Other Liabilities | Standard Representations And Warranties Related To Loan Sales To Government-Sponsored Agencies
Loss Contingencies [Line Items]
Loss contingency accrual	1,300,000		$ 1,500,000
Settled Litigation
Loss Contingencies [Line Items]
Settlement awarded to other party	98,000,000
Damages sought	$ 79,000,000
Intellectual Ventures II, LLC vs BBVA Compass Bancshares, Inc | Pending Litigation
Loss Contingencies [Line Items]
Loss contingency, patents allegedly infringed | patent		5