Securities (Tables)

9 Months Ended

Sep. 30, 2016

Gain (Loss) on Investments [Line Items]

Amortized Cost and Fair Value of Securities Available for Sale

Securities Available for Sale
(in thousands)	September 30, 2016								December 31, 2015
			Gross		Gross						Gross		Gross
	Amortized		Unrealized		Unrealized		Fair		Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value		Cost		Gains		Losses		Value
US Treasury and government agency securities	$	20,604	$	67	$	—	$	20,671	$	135	$	—	$	1	$	134
Municipal obligations		214,403		3,024		409		217,018		39,410		235		38		39,607
Residential mortgage-backed securities		1,737,812		38,204		91		1,775,925		1,750,168		19,387		11,182		1,758,373
Commercial mortgage-backed securities		172,525		687		103		173,109		—		—		—		—
Collateralized mortgage obligations		220,912		2,344		—		223,256		291,085		140		2,192		289,033
Corporate debt securities		3,500		—		—		3,500		3,500		—		—		3,500
Equity securities		865		336		—		1,201		2,447		358		48		2,757
	$	2,370,621	$	44,662	$	603	$	2,414,680	$	2,086,745	$	20,120	$	13,461	$	2,093,404

Amortized Cost and Fair Value of Securities Held to Maturity

Securities Held to Maturity
(in thousands)	September 30, 2016								December 31, 2015
			Gross		Gross						Gross		Gross
	Amortized		Unrealized		Unrealized		Fair		Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value		Cost		Gains		Losses		Value
US Treasury and government agency securities	$	50,000	$	860	$	—	$	50,860	$	50,000	$	—	$	410	$	49,590
Municipal obligations		541,839		11,182		1,462		551,559		185,890		3,475		1,166		188,199
Residential mortgage-backed securities		903,703		36,200		—		939,903		1,014,135		15,585		1,589		1,028,131
Collateralized mortgage obligations		932,890		8,767		1,439		940,218		1,120,363		2,244		12,676		1,109,931
	$	2,428,432	$	57,009	$	2,901	$	2,482,540	$	2,370,388	$	21,304	$	15,841	$	2,375,851

Amortized Cost and Fair Value of Debt Securities by Contractual Maturity

(in thousands)	Amortized		Fair
Debt Securities Available for Sale	Cost		Value
Due in one year or less	$	4,864	$	4,900
Due after one year through five years		47,593		48,597
Due after five years through ten years		609,897		621,549
Due after ten years		1,707,402		1,738,433
Total available for sale debt securities	$	2,369,756	$	2,413,479
	Amortized		Fair
Debt Securities Held to Maturity	Cost		Value
Due in one year or less	$	14,982	$	15,019
Due after one year through five years		135,330		138,737
Due after five years through ten years		510,536		517,652
Due after ten years		1,767,584		1,811,132
Total held to maturity securities	$	2,428,432	$	2,482,540

Available for Sale [Member]

Gain (Loss) on Investments [Line Items]

Securities with Unrealized Losses

Available for Sale
September 30, 2016	Losses < 12 months				Losses 12 months or >				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(in thousands)	Value		Losses		Value		Losses		Value		Losses
Municipal obligations	$	69,801		409	$	—		—	$	69,801	$	409
Residential mortgage-backed securities		6,653		55		4,534		36		11,187		91
Commercial mortgage-backed securities		31,640		103		—		—		31,640		103
Collateralized mortgage obligations		6,910		—		—		—		6,910		—
	$	115,004	$	567	$	4,534	$	36	$	119,538	$	603

Available for Sale
December 31, 2015	Losses < 12 months				Losses 12 months or >				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(in thousands)	Value		Losses		Value		Losses		Value		Losses
US Treasury and government agency securities	$	—	$	—	$	82	$	1	$	82	$	1
Municipal obligations		8,296		38		—		—		8,296		38
Residential mortgage-backed securities		831,156		8,257		116,126		2,925		947,282		11,182
Collateralized mortgage obligations		208,397		1,257		33,138		935		241,535		2,192
Equity securities		20		1		1,473		47		1,493		48
	$	1,047,869	$	9,553	$	150,819	$	3,908	$	1,198,688	$	13,461

Held to Maturity [Member]

Gain (Loss) on Investments [Line Items]

Securities with Unrealized Losses

Held to maturity
September 30, 2016	Losses < 12 months				Losses 12 months or >				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(in thousands)	Value		Losses		Value		Losses		Value		Losses
Municipal obligations	$	98,295	$	1,035	$	11,843	$	427	$	110,138	$	1,462
Collateralized mortgage obligations		119,172		146		132,960		1,293		252,132		1,439
	$	217,467	$	1,181	$	144,803	$	1,720	$	362,270	$	2,901

Held to maturity
December 31, 2015	Losses < 12 months				Losses 12 months or >				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(in thousands)	Value		Losses		Value		Losses		Value		Losses
U.S. Treasury and government agency securities	$	45,590	$	410	$	—	$	—	$	45,590	$	410
Municipal obligations		22,652		301		48,727		865		71,379		1,166
Residential mortgage-backed securities		349,635		1,589		—		—		349,635		1,589
Collateralized mortgage obligations		516,330		2,894		370,756		9,782		887,086		12,676
	$	934,207	$	5,194	$	419,483	$	10,647	$	1,353,690	$	15,841