Investment Securities - Investment Securities by Credit Rating Type (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	$ 1,520,237	$ 1,370,696
Investment securities - measured at fair value	1,858	3,036
Securities held to maturity Total, Amortized Cost	0	283,006
Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	299,037	115,665
Securities held to maturity Total, Amortized Cost		183,579
Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	891,189	1,021,421
Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	2,147
Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	70,243	36,099
Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	5,149	5,433
Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	37,702	36,532
U.S. Government-sponsored agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	18,346	46,975
Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	82,612	61,484
Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	25,546	23,805
Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	11,445
Securities held to maturity Total, Amortized Cost		50
CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	24,332	23,282
Securities held to maturity Total, Amortized Cost		1,600
Rated Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	1,520,237	1,370,696
Securities held to maturity Total, Amortized Cost		283,006
Rated Securities [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	299,037	115,665
Securities held to maturity Total, Amortized Cost		183,579
Rated Securities [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	891,189	1,021,421
Investment securities - measured at fair value	1,858	3,036
Rated Securities [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	2,147
Rated Securities [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	70,243	36,099
Rated Securities [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	5,149	5,433
Rated Securities [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	37,702	36,532
Rated Securities [Member] | U.S. Government-sponsored agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	18,346	46,975
Rated Securities [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	82,612	61,484
Rated Securities [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	25,546	23,805
Rated Securities [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	11,445
Securities held to maturity Total, Amortized Cost		50
Rated Securities [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	52,489
Securities held to maturity Total, Amortized Cost		97,777
Rated Securities [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	24,332	23,282
Securities held to maturity Total, Amortized Cost		1,600
AAA [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	73,261	29,079
Securities held to maturity Total, Amortized Cost		7,965
AAA [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	8,168	0
Securities held to maturity Total, Amortized Cost		7,965
AAA [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Investment securities - measured at fair value	0	0
AAA [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
AAA [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	59,944	23,646
AAA [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	5,149	5,433
AAA [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
AAA [Member] | U.S. Government-sponsored agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
AAA [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
AAA [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
AAA [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
Securities held to maturity Total, Amortized Cost		0
AAA [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
Securities held to maturity Total, Amortized Cost		0
AAA [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Securities held to maturity Total, Amortized Cost		0
Split-rated AAA/AA Plus [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	911,682	1,068,396
Securities held to maturity Total, Amortized Cost		0
Split-rated AAA/AA Plus [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Securities held to maturity Total, Amortized Cost		0
Split-rated AAA/AA Plus [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	891,189	1,021,421
Investment securities - measured at fair value	1,858	3,036
Split-rated AAA/AA Plus [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	2,147
Split-rated AAA/AA Plus [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Split-rated AAA/AA Plus [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Split-rated AAA/AA Plus [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Split-rated AAA/AA Plus [Member] | U.S. Government-sponsored agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	18,346	46,975
Split-rated AAA/AA Plus [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Split-rated AAA/AA Plus [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Split-rated AAA/AA Plus [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
Securities held to maturity Total, Amortized Cost		0
Split-rated AAA/AA Plus [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
Securities held to maturity Total, Amortized Cost		0
Split-rated AAA/AA Plus [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Securities held to maturity Total, Amortized Cost		0
AA Plus to AA- [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	141,083	58,186
Securities held to maturity Total, Amortized Cost		74,446
AA Plus to AA- [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	138,256	58,061
Securities held to maturity Total, Amortized Cost		71,749
AA Plus to AA- [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Investment securities - measured at fair value	0	0
AA Plus to AA- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
AA Plus to AA- [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	68	125
AA Plus to AA- [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
AA Plus to AA- [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
AA Plus to AA- [Member] | U.S. Government-sponsored agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
AA Plus to AA- [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
AA Plus to AA- [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
AA Plus to AA- [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
Securities held to maturity Total, Amortized Cost		0
AA Plus to AA- [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	2,759
Securities held to maturity Total, Amortized Cost		2,697
AA Plus to AA- [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Securities held to maturity Total, Amortized Cost		0
A Plus to A- [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	155,164	61,490
Securities held to maturity Total, Amortized Cost		131,662
A Plus to A- [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	146,155	57,389
Securities held to maturity Total, Amortized Cost		96,560
A Plus to A- [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Investment securities - measured at fair value	0	0
A Plus to A- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
A Plus to A- [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	3,439	4,101
A Plus to A- [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
A Plus to A- [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
A Plus to A- [Member] | U.S. Government-sponsored agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
A Plus to A- [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
A Plus to A- [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
A Plus to A- [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
Securities held to maturity Total, Amortized Cost		0
A Plus to A- [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	5,570
Securities held to maturity Total, Amortized Cost		35,102
A Plus to A- [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Securities held to maturity Total, Amortized Cost		0
BBB Plus to BBB- [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	171,851	110,809
Securities held to maturity Total, Amortized Cost		67,283
BBB Plus to BBB- [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	6,263	0
Securities held to maturity Total, Amortized Cost		7,305
BBB Plus to BBB- [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Investment securities - measured at fair value	0	0
BBB Plus to BBB- [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
BBB Plus to BBB- [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	3,595	4,625
BBB Plus to BBB- [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
BBB Plus to BBB- [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	37,702	36,532
BBB Plus to BBB- [Member] | U.S. Government-sponsored agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
BBB Plus to BBB- [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	54,585	45,847
BBB Plus to BBB- [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	25,546	23,805
BBB Plus to BBB- [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
Securities held to maturity Total, Amortized Cost		0
BBB Plus to BBB- [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	44,160
Securities held to maturity Total, Amortized Cost		59,978
BBB Plus to BBB- [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Securities held to maturity Total, Amortized Cost		0
BB Plus and below [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	32,469	17,061
Securities held to maturity Total, Amortized Cost		50
BB Plus and below [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	195	215
Securities held to maturity Total, Amortized Cost		0
BB Plus and below [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Investment securities - measured at fair value	0	0
BB Plus and below [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
BB Plus and below [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	3,197	3,602
BB Plus and below [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
BB Plus and below [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
BB Plus and below [Member] | U.S. Government-sponsored agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
BB Plus and below [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	17,632	13,244
BB Plus and below [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
BB Plus and below [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	11,445
Securities held to maturity Total, Amortized Cost		50
BB Plus and below [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
Securities held to maturity Total, Amortized Cost		0
BB Plus and below [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Securities held to maturity Total, Amortized Cost		0
Corporate Credit Quality Indicator Unrated [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	34,727	25,675
Securities held to maturity Total, Amortized Cost		1,600
Corporate Credit Quality Indicator Unrated [Member] | Municipal obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Securities held to maturity Total, Amortized Cost		0
Corporate Credit Quality Indicator Unrated [Member] | Residential mortgage-backed securities issued by GSEs
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Investment securities - measured at fair value	0	0
Corporate Credit Quality Indicator Unrated [Member] | Commercial Mortgage Backed Securities Issued By US Government Sponsored Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
Corporate Credit Quality Indicator Unrated [Member] | Private label residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Corporate Credit Quality Indicator Unrated [Member] | Private label commercial mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Corporate Credit Quality Indicator Unrated [Member] | Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Corporate Credit Quality Indicator Unrated [Member] | U.S. Government-sponsored agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Corporate Credit Quality Indicator Unrated [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	10,395	2,393
Corporate Credit Quality Indicator Unrated [Member] | Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0	0
Corporate Credit Quality Indicator Unrated [Member] | Collateralized debt obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
Securities held to maturity Total, Amortized Cost		0
Corporate Credit Quality Indicator Unrated [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	0
Securities held to maturity Total, Amortized Cost		0
Corporate Credit Quality Indicator Unrated [Member] | CRA investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities - AFS, at fair value; amortized cost of $1,493,648 at December 31, 2014 and $1,404,048 at December 31, 2013	24,332	23,282
Securities held to maturity Total, Amortized Cost		$ 1,600