Securities Available for Sale (Tables)

3 Months Ended

Mar. 31, 2017

Available-for-sale Securities [Abstract]

Summary of Securities Available for Sale

The following is a summary of securities available for sale as of the dates indicated:



	At March 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(Dollars in thousands)
Debt securities:
U.S. Government agency and U.S. Government sponsored enterprises
Debt securities	$	10,002	$	—	$	(4	)	$	9,998
Collateralized mortgage obligations (residential)	736,000		406		(9,787		)	726,619
Mortgage-backed securities (residential)	744,654		1,252		(13,214		)	732,692
Corporate securities	4,564		—		(251		)	4,313
Municipal securities	97,689		609		(1,044		)	97,254
Total debt securities	1,592,909		2,267		(24,300		)	1,570,876
Mutual funds	13,425		18		(373		)	13,070
Total investment securities available for sale	$	1,606,334	$	2,285	$	(24,673	)	$	1,583,946

	At December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(Dollars in thousands)
Debt securities:
U.S. Government agency and U.S. Government sponsored enterprises
Debt securities	$	12,005	$	3	$	—		$	12,008
Collateralized mortgage obligations (residential)	715,981		349		(10,663		)	705,667
Mortgage-backed securities (residential)	741,304		1,132		(14,395		)	728,041
Corporate securities	11,576		—		(449		)	11,127
Municipal securities	88,018		358		(1,537		)	86,839
Total debt securities	1,568,884		1,842		(27,044		)	1,543,682
Mutual funds	13,425		—		(367		)	13,058
Total investment securities available for sale	$	1,582,309	$	1,842	$	(27,411	)	$	1,556,740

Investments Classified by Contractual Maturity Date

The amortized cost and estimated fair value of investment securities at March 31, 2017, by contractual maturity, are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Securities not due at a single maturity date are shown separately.



	Amortized Cost		Estimated Fair Value
	(Dollars in thousands)
Available for sale:
Due within one year	$	10,724	$	10,725
Due after one year through five years	7,472		7,630
Due after five years through ten years	40,905		40,891
Due after ten years	53,154		52,319
U.S. Government agency and U.S. Government sponsored enterprises
Collateralized mortgage obligations (residential)	736,000		726,619
Mortgage-backed securities (residential)	744,654		732,692
Mutual funds	13,425		13,070
Total	$	1,606,334	$	1,583,946

Schedule of Unrealized Loss on Investments

The following tables show our investments’ gross unrealized losses and estimated fair value, aggregated by investment category and the length of time that the individual securities have been in a continuous unrealized loss position as of the dates indicated.



	As of March 31, 2017
	Less than 12 months						12 months or longer						Total
Description of Securities	Number of Securities	Fair Value		Gross Unrealized Losses			Number of Securities	Fair Value		Gross Unrealized Losses			Number of Securities	Fair Value		Gross Unrealized Losses
	(Dollars in thousands)
Debt securities*	3	$	9,998	$	(4	)	—	$	—	$	—		3	$	9,998	$	(4	)
Collateralized mortgage obligations (residential)*	67	624,327		(8,668		)	4	34,843		(1,119		)	71	659,170		(9,787		)
Mortgage-backed securities (residential)*	59	606,378		(13,214		)	—	—		—			59	606,378		(13,214		)
Corporate securities	—	—		—			1	4,313		(251		)	1	4,313		(251		)
Municipal securities	54	50,447		(1,018		)	1	509		(26		)	55	50,956		(1,044		)
Mutual funds	3	11,590		(373		)	—	—		—			3	11,590		(373		)
Total	186	$	1,302,740	$	(23,277	)	6	$	39,665	$	(1,396	)	192	$	1,342,405	$	(24,673	)

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* Investments in U.S. Government agency and U.S. Government sponsored enterprises



	As of December 31, 2016
	Less than 12 months						12 months or longer						Total
Description of Securities	Number of Securities	Fair Value		Gross Unrealized Losses			Number of Securities	Fair Value		Gross Unrealized Losses			Number of Securities	Fair Value		Gross Unrealized Losses
	(Dollars in thousands)
Collateralized mortgage obligations (residential)*	66	$	615,803	$	(9,459	)	4	$	36,333	$	(1,204	)	70	$	652,136	$	(10,663	)
Mortgage-backed securities (residential)*	57	622,797		(14,395		)	—	—		—			57	622,797		(14,395		)
Corporate securities	1	7,014		(2		)	1	4,113		(447		)	2	11,127		(449		)
Municipal securities	95	69,331		(1,537		)	—	—		—			95	69,331		(1,537		)
Mutual funds	3	13,058		(367		)	—	—		—			3	13,058		(367		)
Total	222	$	1,328,003	$	(25,760	)	5	$	40,446	$	(1,651	)	227	$	1,368,449	$	(27,411	)

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* Investments in U.S. Government agency and U.S. Government sponsored enterprises