SECURITIES (Tables)

6 Months Ended

Jun. 30, 2017

Investments, Debt and Equity Securities [Abstract]

Schedule of Amortized Cost and Fair Value of Securities Available for Sale

The amortized cost and fair value of securities are as follows:

(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Securities Available for Sale (AFS):
June 30, 2017
U.S. Treasury	$	29,942	$	7	$	—		$	29,949
U.S. government-sponsored entities	382,668		518		(2,853		)	380,333
Residential mortgage-backed securities:
Agency mortgage-backed securities	1,672,304		3,116		(9,913		)	1,665,507
Agency collateralized mortgage obligations	483,556		284		(9,373		)	474,467
Non-agency collateralized mortgage obligations	2		—		—			2
Commercial mortgage-backed securities	315		—		—			315
States of the U.S. and political subdivisions	31,048		49		(27		)	31,070
Other debt securities	9,878		39		(229		)	9,688
Total debt securities	2,609,713		4,013		(22,395		)	2,591,331
Equity securities	1,696		495		(67		)	2,124
Total securities available for sale	$	2,611,409	$	4,508	$	(22,462	)	$	2,593,455
December 31, 2016
U.S. Treasury	$	29,874	$	79	$	—		$	29,953
U.S. government-sponsored entities	367,604		864		(3,370		)	365,098
Residential mortgage-backed securities:
Agency mortgage-backed securities	1,267,535		2,257		(16,994		)	1,252,798
Agency collateralized mortgage obligations	546,659		419		(11,104		)	535,974
Non-agency collateralized mortgage obligations	891		6		—			897
Commercial mortgage-backed securities	1,292		—		(1		)	1,291
States of the U.S. and political subdivisions	36,065		86		(302		)	35,849
Other debt securities	9,828		94		(435		)	9,487
Total debt securities	2,259,748		3,805		(32,206		)	2,231,347
Equity securities	273		367		—			640
Total securities available for sale	$	2,260,021	$	4,172	$	(32,206	)	$	2,231,987

Schedule of Amortized Cost and Fair Value of Securities Held to Maturity

(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Securities Held to Maturity (HTM):
June 30, 2017
U.S. Treasury	$	500	$	144	$	—		$	644
U.S. government-sponsored entities	247,537		327		(3,704		)	244,160
Residential mortgage-backed securities:
Agency mortgage-backed securities	1,238,720		8,047		(5,561		)	1,241,206
Agency collateralized mortgage obligations	757,780		1,122		(14,066		)	744,836
Commercial mortgage-backed securities	81,455		903		(279		)	82,079
States of the U.S. and political subdivisions	749,642		8,560		(11,904		)	746,298
Total securities held to maturity	$	3,075,634	$	19,103	$	(35,514	)	$	3,059,223
December 31, 2016
U.S. Treasury	$	500	$	137	$	—		$	637
U.S. government-sponsored entities	272,645		348		(4,475		)	268,518
Residential mortgage-backed securities:
Agency mortgage-backed securities	852,215		5,654		(8,645		)	849,224
Agency collateralized mortgage obligations	743,148		447		(17,801		)	725,794
Non-agency collateralized mortgage obligations	1,689		3		(6		)	1,686
Commercial mortgage-backed securities	49,797		181		(226		)	49,752
States of the U.S. and political subdivisions	417,348		1,456		(19,638		)	399,166
Total securities held to maturity	$	2,337,342	$	8,226	$	(50,791	)	$	2,294,777

Gross Gains and Gross Losses Realized on Sales of Securities

Gross gains and gross losses were realized on securities as follows:

	Three Months Ended June 30,						Six Months Ended June 30, 2017
(in thousands)	2017			2016			2017			2016
Gross gains	$	611		$	227		$	4,011		$	298
Gross losses	(118		)	(1		)	(893		)	(1		)
Net gains	$	493		$	226		$	3,118		$	297

Amortized Cost and Fair Value of Securities, by Contractual Maturities

As of June 30, 2017, the amortized cost and fair value of securities, by contractual maturities, were as follows:

	Available for Sale				Held to Maturity
(in thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	105,257	$	105,295	$	612	$	618
Due from one to five years	325,946		323,633		253,083		249,675
Due from five to ten years	19,367		19,317		68,554		69,711
Due after ten years	2,966		2,795		675,430		671,098
	453,536		451,040		997,679		991,102
Residential mortgage-backed securities:
Agency mortgage-backed securities	1,672,304		1,665,507		1,238,720		1,241,206
Agency collateralized mortgage obligations	483,556		474,467		757,780		744,836
Non-agency collateralized mortgage obligations	2		2		—		—
Commercial mortgage-backed securities	315		315		81,455		82,079
Equity securities	1,696		2,124		—		—
Total securities	$	2,611,409	$	2,593,455	$	3,075,634	$	3,059,223

Schedule of Securities Pledged as Collateral

Following is information relating to securities pledged:

(dollars in thousands)	June 30, 2017			December 31, 2016
Securities pledged (carrying value):
To secure public deposits, trust deposits and for other purposes as required by law	$	3,058,009		$	2,779,335
As collateral for short-term borrowings	299,651			322,038
Securities pledged as a percent of total securities	59.2		%	67.9		%

Summaries of Fair Values and Unrealized Losses of Impaired Securities, Segregated by Length of Impairment

Following are summaries of the fair values and unrealized losses of temporarily impaired securities, segregated by length of impairment:

	Less than 12 Months						12 Months or More						Total
(dollars in thousands)	#	Fair Value		Unrealized Losses			#	Fair Value		Unrealized Losses			#	Fair Value		Unrealized Losses
Securities Available for Sale
June 30, 2017
U.S. government-sponsored entities	13	$	237,159	$	(2,853	)	—	$	—	$	—		13	$	237,159	$	(2,853	)
Residential mortgage-backed securities:
Agency mortgage-backed securities	57	1,185,412		(9,913		)	—	—		—			57	1,185,412		(9,913		)
Agency collateralized mortgage obligations	35	302,658		(5,864		)	10	90,687		(3,509		)	45	393,345		(9,373		)
Non-agency collateralized mortgage obligations	1	2		—			—	—		—			1	2		—
Commercial mortgage-backed securities	1	315		—			—	—		—			1	315		—
States of the U.S. and political subdivisions	9	14,906		(19		)	3	3,839		(8		)	12	18,745		(27		)
Other debt securities	—	—		—			3	4,680		(229		)	3	4,680		(229		)
Equity securities	3	1,219		(67		)	—	—		—			3	1,219		(67		)
Total temporarily impaired securities AFS	119	$	1,741,671	$	(18,716	)	16	$	99,206	$	(3,746	)	135	$	1,840,877	$	(22,462	)
December 31, 2016
U.S. government-sponsored entities	11	$	211,636	$	(3,370	)	—	$	—	$	—		11	$	211,636	$	(3,370	)
Residential mortgage-backed securities:
Agency mortgage-backed securities	55	1,056,731		(16,994		)	—	—		—			55	1,056,731		(16,994		)
Agency collateralized mortgage obligations	26	346,662		(7,261		)	9	89,040		(3,843		)	35	435,702		(11,104		)
Commercial mortgage-backed securities	1	1,291		(1		)	—	—		—			1	1,291		(1		)
States of the U.S. and political subdivisions	20	28,631		(302		)	—	—		—			20	28,631		(302		)
Other debt securities	—	—		—			3	4,470		(435		)	3	4,470		(435		)
Total temporarily impaired securities AFS	113	$	1,644,951	$	(27,928	)	12	$	93,510	$	(4,278	)	125	$	1,738,461	$	(32,206	)

	Less than 12 Months						12 Months or More						Total
(dollars in thousands)	#	Fair Value		Unrealized Losses			#	Fair Value		Unrealized Losses			#	Fair Value		Unrealized Losses
Securities Held to Maturity
June 30, 2017
U.S. government-sponsored entities	11	$	201,295	$	(3,704	)	—	$	—	$	—		11	$	201,295	$	(3,704	)
Residential mortgage-backed securities:
Agency mortgage-backed securities	37	668,448		(5,561		)	—	—		—			37	668,448		(5,561		)
Agency collateralized mortgage obligations	29	470,354		(11,451		)	11	91,676		(2,615		)	40	562,030		(14,066		)
Commercial mortgage-backed securities	3	14,839		(52		)	1	7,640		(227		)	4	22,479		(279		)
States of the U.S. and political subdivisions	58	176,763		(11,904		)	—	—		—			58	176,763		(11,904		)
Total temporarily impaired securities HTM	138	$	1,531,699	$	(32,672	)	12	$	99,316	$	(2,842	)	150	$	1,631,015	$	(35,514	)
December 31, 2016
U.S. government-sponsored entities	10	$	185,525	$	(4,475	)	—	$	—	$	—		10	$	185,525	$	(4,475	)
Residential mortgage-backed securities:
Agency mortgage-backed securities	36	551,404		(8,645		)	—	—		—			36	551,404		(8,645		)
Agency collateralized mortgage obligations	29	516,237		(13,710		)	12	112,690		(4,091		)	41	628,927		(17,801		)
Non-agency collateralized mortgage obligations	3	1,128		(6		)	—	—		—			3	1,128		(6		)
Commercial mortgage-backed securities	1	12,317		(10		)	1	8,267		(216		)	2	20,584		(226		)
States of the U.S. and political subdivisions	94	247,301		(19,638		)	—	—		—			94	247,301		(19,638		)
Total temporarily impaired securities HTM	173	$	1,513,912	$	(46,484	)	13	$	120,957	$	(4,307	)	186	$	1,634,869	$	(50,791	)