Related Party Transactions (Details) - USD ($)	1 Months Ended	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Aug. 01, 2014	Mar. 16, 2012
Related Party Transaction [Line Items]
Securities purchased under agreements to resell	$ 197,265,000	$ 197,265,000		$ 279,106,000
Securities sold under agreements to repurchase	148,291,000	148,291,000		76,609,000
FHLB and other borrowings	4,383,454,000	4,383,454,000		5,438,620,000
Preferred stock	229,475,000	229,475,000		229,475,000
Preferred stock dividends		3,219,000
BSI | Line of Credit | BBVA Compass Bancshares, Inc.
Related Party Transaction [Line Items]
Due from related parties	150,000,000	150,000,000		150,000,000	$ 150,000,000
BSI | Revolving Credit Facility | Line of Credit | BBVA Compass Bancshares, Inc.
Related Party Transaction [Line Items]
Due from related parties						$ 420,000,000
BBVA
Related Party Transaction [Line Items]
Securities purchased under agreements to resell	94,915,000	94,915,000		26,404,000
Securities sold under agreements to repurchase	81,618,000	81,618,000		74,049,000
BBVA | BBVA Compass Bancshares, Inc.
Related Party Transaction [Line Items]
Fees on agreements		6,800,000	$ 6,300,000
Revenue from related parties		3,900,000	2,400,000
Fair value hedges | BBVA
Related Party Transaction [Line Items]
Related party transaction, amount of transaction	24,597,000	24,597,000		(9,405,000)
Derivatives designated as hedging instrument | BBVA
Related Party Transaction [Line Items]
Derivative, notional amount	4,900,000,000	4,900,000,000		5,300,000,000
Free-standing derivatives not designated as hedging instrument | Free-standing derivative instruments – risk management and other purposes | BBVA
Related Party Transaction [Line Items]
Related party transaction, amount of transaction	(50,944,000)	(50,944,000)		(20,082,000)
Revolving Note And Cash Subordinated Agreement | BSI | BBVA Compass Bancshares, Inc.
Related Party Transaction [Line Items]
FHLB and other borrowings	0	0		$ 0
Interest expense		822,000	$ 552,000
Commercial Loan | BBVA | BBVA New York [Member]
Related Party Transaction [Line Items]
Revenue from related parties	444,000,000
Other Noninterest Income | Commercial Loan | BBVA | BBVA New York [Member]
Related Party Transaction [Line Items]
Related party transaction amount	1,500,000
Preferred Stock | Series A Preferred Stock [Member] | BBVA
Related Party Transaction [Line Items]
Preferred stock	$ 229,000,000	229,000,000
Preferred stock dividends		$ 3,200,000