Investment Securities (Tables)

9 Months Ended

Sep. 30, 2017

Investment Securities

Schedule of amortized cost and fair value of securities

	September 30, 2017								December 31, 2016
	Amortized		Unrealized		Unrealized		Fair		Amortized		Unrealized		Unrealized		Fair
(dollars in thousands)	Cost		Gains		Losses		Value		Cost		Gains		Losses		Value
U.S. Treasury securities	$	404,693	$	—	$	(7,927)	$	396,766	$	405,637	$	—	$	(13,164)	$	392,473
Government-sponsored enterprises debt securities		249,711		26		(4,599)		245,138		249,707		16		(7,056)		242,667
Government agency mortgage-backed securities		163,289		—		(3,502)		159,787		190,485		—		(4,822)		185,663
Government-sponsored enterprises mortgage-backed securities		186,957		234		(3,052)		184,139		208,034		385		(4,034)		204,385
Non-government asset-backed securities		101		—		—		101		12,592		—		(9)		12,583
Collateralized mortgage obligations:
Government agency		3,551,654		1,129		(38,879)		3,513,904		3,409,822		794		(58,794)		3,351,822
Government-sponsored enterprises		824,664		1,529		(11,055)		815,138		700,338		789		(13,206)		687,921
Total available-for-sale securities	$	5,381,069	$	2,918	$	(69,014)	$	5,314,973	$	5,176,615	$	1,984	$	(101,085)	$	5,077,514

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

	September 30, 2017
	Amortized		Fair
(dollars in thousands)	Cost		Value
Due after one year through five years	$	330,821	$	323,769
Due after five years through ten years		323,583		318,135
		654,404		641,904
Government agency mortgage-backed securities		163,289		159,787
Government-sponsored enterprises mortgage-backed securities		186,957		184,139
Non-government asset-backed securities		101		101
Collateralized mortgage obligations:
Government agency		3,551,654		3,513,904
Government-sponsored enterprises		824,664		815,138
Total mortgage- and asset-backed securities		4,726,665		4,673,069
Total available-for-sale securities	$	5,381,069	$	5,314,973

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

	Time in Continuous Loss as of September 30, 2017
	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 securities	$	(802)	$	97,031	$	(7,125)	$	299,735	$	(7,927)	$	396,766
Government-sponsored enterprises debt securities		(1,471)		111,554		(3,128)		98,558		(4,599)		210,112
Government agency mortgage-backed securities		(2,080)		111,991		(1,422)		47,796		(3,502)		159,787
Government-sponsored enterprises mortgage-backed securities		(441)		36,211		(2,611)		141,003		(3,052)		177,214
Collateralized mortgage obligations:
Government agency		(12,237)		1,589,897		(26,642)		1,336,841		(38,879)		2,926,738
Government-sponsored enterprises		(2,274)		319,802		(8,781)		241,718		(11,055)		561,520
Total available-for-sale securities with unrealized losses	$	(19,305)	$	2,266,486	$	(49,709)	$	2,165,651	$	(69,014)	$	4,432,137

	Time in Continuous Loss as of December 31, 2016
	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 securities	$	(13,164)	$	392,473	$	—	$	—	$	(13,164)	$	392,473
Government-sponsored enterprises debt securities		(7,056)		207,651		—		—		(7,056)		207,651
Government agency mortgage-backed securities		(4,822)		185,663		—		—		(4,822)		185,663
Government-sponsored enterprises mortgage-backed securities		(4,034)		195,848		—		—		(4,034)		195,848
Non-government asset-backed securities		(3)		5,202		(6)		7,381		(9)		12,583
Collateralized mortgage obligations:
Government agency		(51,484)		2,847,103		(7,310)		233,706		(58,794)		3,080,809
Government-sponsored enterprises		(1,807)		252,065		(11,399)		279,282		(13,206)		531,347
Total available-for-sale securities with unrealized losses	$	(82,370)	$	4,086,005	$	(18,715)	$	520,369	$	(101,085)	$	4,606,374