Investment Securities (Tables)

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Schedule of Debt Securities

The amortized cost and fair value of investment securities were as follows:

	Investment Securities Available-for-sale, At Fair Value
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
At December 31, 2019
Debt securities:
Government and government-sponsored enterprises	$	235,045	$	18	$	678	$	234,385
Obligations of states and political subdivisions	852,096		12,446		687		863,855
Mortgage-backed securities:
Residential agency	4,492,427		68,797		6,103		4,555,121
Residential non-agency	374,046		1,166		616		374,596
Commercial agency	645,814		8,639		2,049		652,404
Commercial non-agency	39,398		17		205		39,210
Total mortgage-backed debt securities	5,551,685		78,619		8,973		5,621,331
Corporate debt and trust preferred securities	451		—		21		430
Total investment securities available-for-sale	$	6,639,277	$	91,083	$	10,359	$	6,720,001
At December 31, 2018
Debt securities:
Obligations of states and political subdivisions	$	566,304	$	46	$	9,479	$	556,871
Mortgage-backed securities:
Residential agency	1,845,451		8,026		26,728		1,826,749
Residential non-agency	4		—		—		4
Commercial agency	85,245		1,196		—		86,441
Total mortgage-backed debt securities	1,930,700		9,222		26,728		1,913,194
Total investment securities available-for-sale	$	2,497,004	$	9,268	$	36,207	$	2,470,065

	Investment Securities Held-to-Maturity
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
At December 31, 2019
Residential agency mortgage-backed securities	$	135,769	$	5,576	$	177	$	141,168
Corporate debt and trust preferred securities	3,676		—		—		3,676
Total investment securities held-to-maturity	$	139,445	$	5,576	$	177	$	144,844
At December 31, 2018
Residential agency mortgage-backed securities	$	146,052	$	1,460	$	1,045	$	146,467
Corporate debt and trust preferred securities	2,800		—		—		2,800
Total investment securities held-to-maturity	$	148,852	$	1,460	$	1,045	$	149,267

Schedule of Gross Unrealized Losses and Fair Value of Debt Securities Available for Sale and Debt Securities Held to Maturity that are in a Loss Position

Gross unrealized losses and fair value of investment securities aggregated by investment category and the length of time the securities were in a continuous loss position were as follows: 

	At December 31, 2019
	Less than 12 months				12 months or more				Total
(In thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Investment securities available-for-sale
Debt securities:
Government and government sponsored enterprises	$	226,177	$	678	$	—	$	—	$	226,177	$	678
Obligations of states and political subdivisions	60,639		687		—		—		60,639		687
Mortgage-backed securities:
Residential agency	667,511		3,586		200,534		2,517		868,045		6,103
Residential non-agency	140,403		616		—		—		140,403		616
Commercial agency	176,880		2,049		—		—		176,880		2,049
Commercial non-agency	25,560		205		—		—		25,560		205
Total mortgage-backed debt securities	1,010,354		6,456		200,534		2,517		1,210,888		8,973
Corporate debt and trust preferred securities	430		21		—		—		430		21
Total investment securities available-for-sale	$	1,297,600	$	7,842	$	200,534	$	2,517	$	1,498,134	$	10,359
Investment securities held-to-maturity
Residential agency mortgage-backed securities	$	7,116	$	72	$	9,209	$	105	$	16,325	$	177
Total investment securities held-to-maturity	$	7,116	$	72	$	9,209	$	105	$	16,325	$	177

	At December 31, 2018
	Less than 12 months				12 months or more				Total
(In thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Investment securities available-for-sale
Debt securities:
Obligations of states and political subdivisions	$	3,620	$	—	$	526,817	$	9,479	$	530,437	$	9,479
Residential agency mortgage-backed securities	102,709		184		838,482		26,544		941,191		26,728
Total investment securities available-for-sale	$	106,329	$	184	$	1,365,299	$	36,023	$	1,471,628	$	36,207
Investment securities held-to-maturity
Residential agency mortgage-backed securities	$	3,074	$	14	$	31,738	$	1,031	$	34,812	$	1,045
Total investment securities held-to-maturity	$	3,074	$	14	$	31,738	$	1,031	$	34,812	$	1,045

Realized Gain (Loss) on Investments

The gross gains and losses on sales of investment securities were as follows: 

	Year Ended December 31,
(In thousands)	2019		2018		2017
Gross realized gains	$	10,877	$	1,148	$	—
Gross realized losses	3,491		1,021		—
Recoveries on previously impaired investment securities held-to-maturity	39		221		237
Net gains on investment securities	$	7,425	$	348	$	237

Schedule of Amortized Cost and Fair Value of Debt Securities Available for Sale and Debt Securities Held to Maturity by Contractual Maturity

The amortized cost and fair value of investment securities by final contractual maturity were as follows. Securities with multiple maturity dates are classified in the period of final maturity. The final contractual maturities do not consider possible prepayments and therefore expected maturities may differ because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

	At December 31, 2019				At December 31, 2018
(In thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Investment Securities Available-for-Sale
Due in one year or less	$	66,124	$	66,112	$	—	$	—
Due in 1-5 years	191,364		192,065		24,464		24,375
Due in 5-10 years	547,813		555,523		509,832		503,768
Due after 10 years	5,833,976		5,906,301		1,962,708		1,941,922
Total investment securities available-for-sale	$	6,639,277	$	6,720,001	$	2,497,004	$	2,470,065
Investment Securities Held-to-Maturity
Due in 1-5 years	$	3,550	$	3,550	$	2,400	$	2,400
Due in 5-10 years	58		64		430		432
Due after 10 years	135,837		141,230		146,022		146,435
Total investment securities held-to-maturity	$	139,445	$	144,844	$	148,852	$	149,267