Investment Securities (Tables)

12 Months Ended

Dec. 31, 2015

Investments, Debt and Equity Securities [Abstract]

Summary of Amortized Cost and Estimated Fair Value of Investment Securities

The majority of securities held are publicly traded, and the estimated fair values were obtained from an independent pricing service based upon market quotes.


	December 31, 2015
	Amortized Cost		Gross Unrealized Holding Gain		Gross Unrealized Holding Loss			Fair Value		Total Percent
	(Dollars in thousands)
Investment securities available-for-sale:
Government agency/GSEs	$	5,752	$	—	$	(7	)	$	5,745		0.24	%
Residential mortgage-backed securities		1,788,857		26,001		(1,761	)		1,813,097		76.55	%
CMOs/REMICs — residential		380,166		4,689		(1,074	)		383,781		16.20	%
Municipal bonds		157,940		3,036		(3	)		160,973		6.80	%
Other securities		5,000		50		—			5,050		0.21	%

Total available-for-sale securities	$	2,337,715	$	33,776	$	(2,845	)	$	2,368,646		100.00	%

Investment securities held-to-maturity (1):
Government agency/GSEs	$	293,338	$	1,176	$	(734	)	$	293,780		34.47	%
Residential mortgage-backed securities		232,053		—		(1,293	)		230,760		27.27	%
CMO		1,284		569		—			1,853		0.15	%
Municipal bonds		324,314		3,051		(719	)		326,646		38.11	%

Total held-to-maturity securities	$	850,989	$	4,796	$	(2,746)		$	853,039		100.00	%


	December 31, 2014
	Amortized Cost		Gross Unrealized Holding Gain		Gross Unrealized Holding Loss			Fair Value		Total Percent
	(Dollars in thousands)
Investment securities available-for-sale:
Government agency/GSEs	$	339,071	$	—	$	(8,228	)	$	330,843		10.55	%
Residential mortgage-backed securities		1,884,370		36,154		(3,028	)		1,917,496		61.12	%
CMOs/REMICs — residential		297,318		7,050		(277	)		304,091		9.69	%
Municipal bonds		557,823		22,463		(645	)		579,641		18.48	%
Other securities		5,000		87		—			5,087		0.16	%

Total available-for-sale securities	$	3,083,582	$	65,754	$	(12,178	)	$	3,137,158		100.00	%

Investment securities held-to-maturity (1):
CMO	$	1,528	$	649	$	—		$	2,177		100.00	%

Total held-to-maturity securities	$	1,528	$	649	$	—		$	2,177		100.00	%

(1)	Securities held-to-maturity are presented in the consolidated balance sheets at amortized cost.

Summary of Interest Income Earned on Investment Securities

The following table provides information about the amount of interest income earned on investment securities which is fully taxable and which is exempt from regular federal income tax.


	For the Year Ended December 31,
	2015		2014		2013
	(Dollars in thousands)
Investment securities available-for-sale:
Taxable	$	48,854	$	47,301	$	28,186
Tax-advantaged		14,336		20,913		22,025
Investment securities held-to-maturity:
Taxable		4,451		164		188
Tax-advantaged		4,567		—		—

Total interest income from investment securities	$	72,208	$	68,378	$	50,399

Summary of Continuous Unrealized Loss Position of Securities

The tables below show the Company’s investment securities’ gross unrealized losses and fair value by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2015 and 2014. Management has reviewed individual securities to determine whether a decline in fair value below the amortized cost basis is other-than-temporary.


	December 31, 2015
	Less Than 12 Months					12 Months or Longer					Total
	Fair Value		Gross Unrealized Holding Losses			Fair Value		Gross Unrealized Holding Losses			Fair Value		Gross Unrealized Holding Losses
	(Dollars in thousands)
Investment securities available-for-sale:
Government agency/GSEs	$	5,745	$	(7	)	$	—	$	—		$	5,745	$	(7	)
Residential mortgage-backed securities		437,699		(1,761	)		—		—			437,699		(1,761	)
CMOs/REMICs — residential		171,923		(1,074	)		—		—			171,923		(1,074	)
Municipal bonds		398		(2	)		5,961		(1	)		6,359		(3	)
Other securities		—		—			—		—			—		—

Total available-for-sale securities	$	615,765	$	(2,844	)	$	5,961	$	(1	)	$	621,726	$	(2,845	)

Investment securities held-to-maturity:
Government agency/GSEs	$	84,495	$	(734	)	$	—	$	—		$	84,495	$	(734	)
Residential mortgage-backed securities		230,760		(1,293	)		—		—			230,760		(1,293	)
CMO		—		—			—		—			—		—
Municipal bonds		110,119		(719	)		—		—			110,119		(719	)
Other securities		—		—			—		—			—		—

Total held-to-maturity securities	$	425,374	$	(2,746	)	$	—	$	—		$	425,374	$	(2,746	)


	December 31, 2014
	Less Than 12 Months				12 Months or Longer				Total
	Fair Value		Gross Unrealized Holding Losses		Fair Value		Gross Unrealized Holding Losses		Fair Value		Gross Unrealized Holding Losses
	(Dollars in thousands)
Investment securities available-for-sale:
Government agency/GSEs	$	22,224	$	28	$	307,873	$	8,200	$	330,097	$	8,228
Residential mortgage-backed securities		19,636		4		145,681		3,024		165,317		3,028
CMOs/REMICs — residential		—		—		31,143		277		31,143		277
Municipal bonds		1,953		23		24,812		622		26,765		645
Other securities		—		—		—		—		—		—

Total available-for-sale securities	$	43,813	$	55	$	509,509	$	12,123	$	553,322	$	12,178

Summary of Amortized Cost and Fair Value of Debt Securities by Contractual Maturity

Mortgage-backed securities and CMOs/REMICs are included in maturity categories based upon estimated prepayment speeds.


	December 31, 2015
	Available-for-sale				Held-to-maturity
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(Dollars in thousands)
Due in one year or less	$	13,758	$	13,980	$	—	$	—
Due after one year through five years		1,967,040		1,993,960		153,226		153,004
Due after five years through ten years		129,268		130,620		376,604		376,113
Due after ten years		227,649		230,086		321,159		323,922

Total investment securities	$	2,337,715	$	2,368,646	$	850,989	$	853,039