The amortized cost, gross unrealized gains and losses, and fair value of investments in fixed income securities classified as available-for-sale at September 30, 2019 and December 31, 2018 are shown in tables 7.1a and 7.1b below.



Details of fixed income securities by category as of September 30, 2019
Table	7.1a
(In thousands)		Amortized Cost		Gross Unrealized Gains		Gross Unrealized (Losses) ⁽¹⁾			Fair Value
U.S. Treasury securities and obligations of U.S. government corporations and agencies		$	197,748	$	1,456	$	(75	)	$	199,129
Obligations of U.S. states and political subdivisions		1,552,283		108,763		(494		)	1,660,552
Corporate debt securities		2,653,124		74,630		(3,151		)	2,724,603
Asset backed securities (“ABS”)		212,792		2,819		(65		)	215,546
Residential mortgage backed securities (“RMBS”)		248,098		1,022		(2,663		)	246,457
Commercial mortgage backed securities (“CMBS”)		280,364		6,714		(266		)	286,812
Collateralized loan obligations (“CLOs”)		329,484		81		(1,672		)	327,893
Total fixed income securities		$	5,473,893	$	195,485	$	(8,386	)	$	5,660,992



Details of fixed income securities by category as of December 31, 2018
Table	7.1b
(In thousands)		Amortized Cost		Gross Unrealized Gains		Gross Unrealized (Losses) ⁽¹⁾			Fair Value
U.S. Treasury securities and obligations of U.S. government corporations and agencies		$	167,655	$	597	$	(1,076	)	$	167,176
Obligations of U.S. states and political subdivisions		1,701,826		29,259		(10,985		)	1,720,100
Corporate debt securities		2,439,173		2,103		(40,514		)	2,400,762
ABS		111,953		226		(146		)	112,033
RMBS		189,238		32		(10,309		)	178,961
CMBS		276,352		888		(9,580		)	267,660
CLOs		310,587		2		(5,294		)	305,295
Total fixed income securities		$	5,196,784	$	33,107	$	(77,904	)	$	5,151,987

The increase in gross unrealized gains and the decrease in gross unrealized losses in our fixed income securities from December 31, 2018 to September 30, 2019 were primarily caused by declines in interest rates during that period.

We had $13.8 million and $13.5 million of investments at fair value on deposit with various states as of September 30, 2019 and December 31, 2018, respectively, due to regulatory requirements of those state insurance departments.

The amortized cost and fair values of fixed income securities at September 30, 2019, by contractual maturity, are shown in table 7.2 below. Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Because most ABS, RMBS, CMBS, and CLOs provide for periodic payments throughout their lives, they are listed in separate categories.



Fixed income securities maturity schedule
Table	7.2
		September 30, 2019
(In thousands)		Amortized cost		Fair Value
Due in one year or less		$	372,478	$	373,388
Due after one year through five years		1,928,972		1,966,387
Due after five years through ten years		1,001,486		1,059,774
Due after ten years		1,100,219		1,184,735
		4,403,155		4,584,284

ABS		212,792		215,546
RMBS		248,098		246,457
CMBS		280,364		286,812
CLOs		329,484		327,893
Total as of September 30, 2019		$	5,473,893	$	5,660,992

Proceeds from sales of fixed income securities classified as available-for-sale were $201.4 million and $338.9 million during the nine months ended September 30, 2019 and 2018, respectively. Gross gains of $3.3 million and $5.3 million and gross losses of $0.7 million and $3.0 million were realized on those sales during the three and nine months ended September 30, 2019, respectively. Gross gains of $0.3 million and $0.4 million and gross losses of $2.3 million and $3.3 million were realized on those sales during the three and nine months ended September 30, 2018, respectively. During the nine months ended September 30, 2019, we recorded other-than-temporary impairment (“OTTI”) losses of $0.1 million. During the three and nine months ended September 30, 2018, we recorded OTTI losses of $0.5 million and $1.8 million, respectively.



Details of equity security investments as of September 30, 2019
Table	7.3a
(In thousands)		Cost		Gross Gains		Gross Losses			Fair Value
Equity securities		$	17,205	$	163	$	(8	)	$	17,360



Details of equity security investments as of December 31, 2018
Table	7.3b
(In thousands)		Cost		Gross Gains		Gross Losses			Fair Value
Equity securities		$	3,993	$	11	$	(72	)	$	3,932

For the three and nine months ended September 30, 2019, we recognized an insignificant amount and $0.2 million, respectively, of net gains on equity securities still held as of September 30, 2019. For the nine months ended September 30, 2018, we recognized $3.6 million of net gains on equity securities still held as of September 30, 2018.

Other invested assets include an investment in Federal Home Loan Bank (“FHLB”) stock that is carried at cost, which due to its nature approximates fair value. Ownership of FHLB stock provides access to a secured lending facility, and our current FHLB Advance amount is secured by eligible collateral whose fair value is maintained at a minimum of 102% of the outstanding principal balance. As of September 30, 2019, that collateral consisted of fixed income securities included in our total investment portfolio, and cash and cash equivalents, with a total fair value of $165.4 million.

Tables 7.4a and 7.4b below summarize, for all available-for-sale investments in an unrealized loss position at September 30, 2019 and December 31, 2018, the aggregate fair value and gross unrealized loss by the length of time those securities have been continuously in an unrealized loss position. The fair value amounts reported in tables 7.4a and 7.4b are estimated using the process described in Note 8 - “Fair Value Measurements” to these consolidated financial statements and in Note 3 - “Significant Accounting Policies” of the notes to the consolidated financial statements in our 2018 Annual Report on Form 10-K.



Unrealized loss aging for securities by type and length of time as of September 30, 2019
Table	7.4a
		Less Than 12 Months					12 Months or Greater					Total
(In thousands)		Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
U.S. Treasury securities and obligations of U.S. government corporations and agencies		$	25,284	$	(48	)	$	7,364	$	(27	)	$	32,648	$	(75	)
Obligations of U.S. states and political subdivisions		4,965		(467		)	10,007		(27		)	14,972		(494		)
Corporate debt securities		135,541		(2,818		)	78,842		(333		)	214,383		(3,151		)
ABS		8,998		(65		)	—		—			8,998		(65		)
RMBS		47,166		(309		)	116,534		(2,354		)	163,700		(2,663		)
CMBS		21,882		(196		)	13,579		(70		)	35,461		(266		)
CLOs		147,272		(1,008		)	113,322		(664		)	260,594		(1,672		)
Total		$	391,108	$	(4,911	)	$	339,648	$	(3,475	)	$	730,756	$	(8,386	)



Unrealized loss aging for securities by type and length of time as of December 31, 2018
Table	7.4b
		Less Than 12 Months					12 Months or Greater					Total
(In thousands)		Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
U.S. Treasury securities and obligations of U.S. government corporations and agencies		$	23,710	$	(15	)	$	69,146	$	(1,061	)	$	92,856	$	(1,076	)
Obligations of U.S. states and political subdivisions		316,655		(3,875		)	358,086		(7,110		)	674,741		(10,985		)
Corporate debt securities		1,272,279		(18,130		)	785,627		(22,384		)	2,057,906		(40,514		)
ABS		51,324		(146		)	—		—			51,324		(146		)
RMBS		24		—			178,573		(10,309		)	178,597		(10,309		)
CMBS		65,704		(1,060		)	163,272		(8,520		)	228,976		(9,580		)
CLOs		296,497		(5,294		)	—		—			296,497		(5,294		)
Total		$	2,026,193	$	(28,520	)	$	1,554,704	$	(49,384	)	$	3,580,897	$	(77,904	)