Investment Securities (Tables)

12 Months Ended

Dec. 31, 2021

Investment Securities

Schedule of amortized cost and fair value of securities

	December 31,
	2021								2020
	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	$	196,662	$	125	$	(4,224)	$	192,563	$	170,123	$	1,359	$	(61)	$	171,421
Mortgage-backed securities:
Residential - Government agency		135,764		1,791		(291)		137,264		155,169		5,293		—		160,462
Residential - Government-sponsored enterprises		1,496,605		6,914		(12,419)		1,491,100		434,282		13,643		(725)		447,200
Commercial - Government agency		392,443		1,741		(6,521)		387,663		583,232		16,537		(119)		599,650
Commercial - Government-sponsored enterprises		1,415,511		2,646		(48,714)		1,369,443		931,095		9,045		(7,983)		932,157
Collateralized mortgage obligations:
Government agency		2,103,187		7,768		(31,432)		2,079,523		1,902,326		32,246		(1,019)		1,933,553
Government-sponsored enterprises		2,671,131		3,608		(53,695)		2,621,044		1,808,804		18,991		(823)		1,826,972
Collateralized loan obligations		105,245		2		—		105,247		—		—		—		—
Debt securities issued by states and political subdivisions		44,185		—		—		44,185		—		—		—		—
Total available-for-sale securities	$	8,560,733	$	24,595	$	(157,296)	$	8,428,032	$	5,985,031	$	97,114	$	(10,730)	$	6,071,415

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

	December 31, 2021
	Amortized		Fair
(dollars in thousands)	Cost		Value
Due in one year or less	$	—	$	—
Due after one year through five years		50,465		50,361
Due after five years through ten years		123,729		121,960
Due after ten years		171,898		169,674
		346,092		341,995
Mortgage-backed securities:
Residential - Government agency		135,764		137,264
Residential - Government-sponsored enterprises		1,496,605		1,491,100
Commercial - Government agency		392,443		387,663
Commercial - Government-sponsored enterprises		1,415,511		1,369,443
Total mortgage-backed securities		3,440,323		3,385,470
Collateralized mortgage obligations:
Government agency		2,103,187		2,079,523
Government-sponsored enterprises		2,671,131		2,621,044
Total collateralized mortgage obligations		4,774,318		4,700,567
Total available-for-sale securities	$	8,560,733	$	8,428,032

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

	Time in Continuous Loss as of December 31, 2021
	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	$	(3,355)	$	134,468	$	(869)	$	16,642	$	(4,224)	$	151,110
Mortgage-backed securities:
Residential - Government agency		(291)		51,231		—		—		(291)		51,231
Residential - Government-sponsored enterprises		(10,876)		1,230,104		(1,543)		32,415		(12,419)		1,262,519
Commercial - Government agency		(5,239)		186,024		(1,282)		26,063		(6,521)		212,087
Commercial - Government-sponsored enterprises		(22,179)		744,819		(26,535)		397,123		(48,714)		1,141,942
Collateralized mortgage obligations:
Government agency		(31,432)		1,441,848		—		—		(31,432)		1,441,848
Government-sponsored enterprises		(52,551)		2,255,535		(1,144)		24,959		(53,695)		2,280,494
Total available-for-sale securities with unrealized losses	$	(125,923)	$	6,044,029	$	(31,373)	$	497,202	$	(157,296)	$	6,541,231

	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