Investment Securities (Tables)

12 Months Ended

Dec. 31, 2020

Investment Securities

Schedule of amortized cost and fair value of securities

	2020								2019
	Amortized		Unrealized		Unrealized		Fair		Amortized		Unrealized		Unrealized		Fair
(dollars in thousands)	Cost		Gains		Losses		Value		Cost		Gains		Losses		Value
U.S. Treasury and government agency debt securities	$	170,123	$	1,359	$	(61)	$	171,421	$	29,832	$	56	$	—	$	29,888
Government-sponsored enterprises debt securities		—		—		—		—		101,697		19		(277)		101,439
Mortgage-backed securities:
Residential - Government agency		155,169		5,293		—		160,462		290,131		2,224		(1,146)		291,209
Residential - Government-sponsored enterprises		434,282		13,643		(725)		447,200		395,039		6,126		(1,673)		399,492
Commercial - Government agency		583,232		16,537		(119)		599,650		—		—		—		—
Commercial - Government-sponsored enterprises		931,095		9,045		(7,983)		932,157		101,798		555		(634)		101,719
Collateralized mortgage obligations:
Government agency		1,902,326		32,246		(1,019)		1,933,553		2,390,143		7,483		(16,348)		2,381,278
Government-sponsored enterprises		1,808,804		18,991		(823)		1,826,972		772,023		2,505		(3,909)		770,619
Total available-for-sale securities	$	5,985,031	$	97,114	$	(10,730)	$	6,071,415	$	4,080,663	$	18,968	$	(23,987)	$	4,075,644

Schedule of amortized cost and fair value of debt securities by contractual maturity

	December 31, 2020
	Amortized		Fair
(dollars in thousands)	Cost		Value
Due in one year or less	$	—	$	—
Due after one year through five years		38,244		38,757
Due after five years through ten years		83,560		84,129
Due after ten years		48,319		48,535
		170,123		171,421
Mortgage-backed securities:
Residential - Government agency		155,169		160,462
Residential - Government-sponsored enterprises		434,282		447,200
Commercial - Government agency		583,232		599,650
Commercial - Government-sponsored enterprises		931,095		932,157
Total mortgage-backed securities		2,103,778		2,139,469
Collateralized mortgage obligations:
Government agency		1,902,326		1,933,553
Government-sponsored enterprises		1,808,804		1,826,972
Total collateralized mortgage obligations		3,711,130		3,760,525
Total available-for-sale securities	$	5,985,031	$	6,071,415

Schedule of gross unrealized losses and fair values of securities in a continuous loss position

	Time in Continuous Loss as of December 31, 2020
	Less Than 12 Months				12 Months or More				Total
	Unrealized				Unrealized				Unrealized
(dollars in thousands)	Losses		Fair Value		Losses		Fair Value		Losses		Fair Value
U.S. Treasury and government agency debt securities	$	(61)	$	38,507	$	—	$	—	$	(61)	$	38,507
Mortgage-backed securities:
Residential - Government-sponsored enterprises		(725)		64,987		—		—		(725)		64,987
Commercial - Government agency		(119)		32,346		—		—		(119)		32,346
Commercial - Government-sponsored enterprises		(7,983)		427,759		—		—		(7,983)		427,759
Collateralized mortgage obligations:
Government agency		(994)		209,124		(25)		6,190		(1,019)		215,314
Government-sponsored enterprises		(823)		296,160		—		—		(823)		296,160
Total available-for-sale securities with unrealized losses	$	(10,705)	$	1,068,883	$	(25)	$	6,190	$	(10,730)	$	1,075,073

	Time in Continuous Loss as of December 31, 2019
	Less Than 12 Months				12 Months or More				Total
	Unrealized				Unrealized				Unrealized
(dollars in thousands)	Losses		Fair Value		Losses		Fair Value		Losses		Fair Value
Government-sponsored enterprises debt securities	$	(277)	$	49,716	$	—	$	—	$	(277)	$	49,716
Mortgage-backed securities:
Residential - Government agency		—		—		(1,146)		109,614		(1,146)		109,614
Residential - Government-sponsored enterprises		(115)		76,481		(1,558)		109,025		(1,673)		185,506
Commercial - Government-sponsored enterprises		(634)		38,062		—		—		(634)		38,062
Collateralized mortgage obligations:
Government agency		(8,049)		969,762		(8,299)		565,764		(16,348)		1,535,526
Government-sponsored enterprises		(583)		180,785		(3,326)		209,752		(3,909)		390,537
Total available-for-sale securities with unrealized losses	$	(9,658)	$	1,314,806	$	(14,329)	$	994,155	$	(23,987)	$	2,308,961