Summary of Investments (Tables)

6 Months Ended

Jun. 30, 2018

Investments, Debt and Equity Securities [Abstract]

Summary of fixed maturity investments classified as available-for-sale and the non-credit related components of other-than-temporary impairments (OTTI) in accumulated other comprehensive income (loss) (AOCI)

The following tables summarize fixed maturity investments classified as available-for-sale and the non-credit-related component of other-than-temporary impairments (“OTTI”) in accumulated other comprehensive income (loss) (“AOCI”):



	June 30, 2018
	Amortized		Gross unrealized		Gross unrealized		Estimated fair value		OTTI (gain) loss
Fixed maturities:	cost		gains		losses		and carrying value		included in AOCI ⁽¹⁾
U.S. government direct obligations and U.S. agencies	$	1,362,245	$	26,310	$	32,382	$	1,356,173	$	—
Obligations of U.S. states and their subdivisions	1,841,971		165,819		4,368		2,003,422		—
Corporate debt securities ⁽²⁾	15,596,700		262,319		420,281		15,438,738		(779		)
Asset-backed securities	1,609,259		68,040		23,498		1,653,801		(36,665		)
Residential mortgage-backed securities	56,655		2,056		886		57,825		(70		)
Commercial mortgage-backed securities	1,358,117		4,899		43,216		1,319,800		—
Collateralized debt obligations	932,625		1,544		1,191		932,978		—
Total fixed maturities	$	22,757,572	$	530,987	$	525,822	$	22,762,737	$	(37,514	)

⁽¹⁾ Indicates the amount of any OTTI (gain) loss included in AOCI that is included in gross unrealized gains and losses. OTTI (gain) loss included in AOCI, as presented above, includes both the initial recognition of non-credit losses and the effects of subsequent increases and decreases in estimated fair value for those fixed maturity securities with previous non-credit impairment. The non-credit loss component of OTTI (gain) loss was in an unrealized gain position due to increases in estimated fair value subsequent to initial recognition of non-credit losses on such securities.

⁽²⁾ Includes perpetual debt investments with amortized cost of $89,267 and estimated fair value of $81,435.



	December 31, 2017
	Amortized		Gross unrealized		Gross unrealized		Estimated fair value		OTTI (gain) loss
Fixed maturities:	cost		gains		losses		and carrying value		included in AOCI ⁽¹⁾
U.S. government direct obligations and U.S. agencies	$	1,837,748	$	41,777	$	7,883	$	1,871,642	$	—
Obligations of U.S. states and their subdivisions	1,872,120		220,507		1,655		2,090,972		—
Corporate debt securities ⁽²⁾	15,234,473		581,991		110,377		15,706,087		(1,018		)
Asset-backed securities	1,622,806		105,301		10,131		1,717,976		(56,735		)
Residential mortgage-backed securities	63,187		2,446		649		64,984		(140		)
Commercial mortgage-backed securities	1,352,906		17,692		12,989		1,357,609		—
Collateralized debt obligations	779,722		4,227		80		783,869		—
Total fixed maturities	$	22,762,962	$	973,941	$	143,764	$	23,593,139	$	(57,893	)

⁽²⁾ Includes perpetual debt investments with amortized cost of $89,267 and estimated fair value of $87,348.

Schedule of amortized cost and estimated fair value of fixed maturity investments classified as available-for-sale

The amortized cost and estimated fair value of fixed maturity investments classified as available-for-sale, by contractual maturity date, are shown in the table below. Actual maturities will likely differ from these projections because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.



	June 30, 2018
	Amortized cost		Estimated fair value
Maturing in one year or less	$	619,874	$	620,381
Maturing after one year through five years	3,447,149		3,441,249
Maturing after five years through ten years	8,216,510		8,066,134
Maturing after ten years	5,500,704		5,670,372
Mortgage-backed and asset-backed securities	4,973,335		4,964,601
Total fixed maturities	$	22,757,572	$	22,762,737

Summary of information regarding the sales of securities classified as available-for-sale

The following table summarizes information regarding the sales of securities classified as available-for-sale:



	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Proceeds from sales	$	511,199	$	891,026	$	1,477,619	$	2,471,548
Gross realized gains from sales	12,452		8,488		24,726		20,921
Gross realized losses from sales	9,789		6,080		16,072		21,337

Summary of activity in the mortgage provision allowance

The following table summarizes activity in the mortgage provision allowance:



	Six Months Ended June 30, 2018		Year Ended December 31, 2017
	Commercial mortgages		Commercial mortgages
Beginning balance	$	773	$	2,882
Provision increases	—		157
Charge-off	—		(663		)
Recovery	—		(30		)
Provision decreases	—		(1,573		)
Ending balance	$	773	$	773

Allowance ending balance by basis of impairment method:
Collectively evaluated for impairment	773		773

Recorded investment balance in the mortgage loan portfolio, gross of allowance, by basis of impairment method:	$	4,316,971	$	4,005,960
Individually evaluated for impairment	2,799		2,942
Collectively evaluated for impairment	4,314,172		4,003,018

Schedule of unrealized investment losses, including the non-credit-related portion of OTTI losses reported in AOCI, by class of investment

The following tables summarize unrealized investment losses, including the non-credit-related portion of OTTI losses reported in AOCI, by class of investment:



	June 30, 2018
	Less than twelve months				Twelve months or longer				Total
	Estimated		Unrealized		Estimated		Unrealized		Estimated		Unrealized
Fixed maturities:	fair value		loss and OTTI		fair value		loss and OTTI		fair value		loss and OTTI
U.S. government direct obligations and U.S. agencies	$	833,130	$	25,923	$	150,012	$	6,459	$	983,142	$	32,382
Obligations of U.S. states and their subdivisions	157,066		1,958		36,003		2,410		193,069		4,368
Corporate debt securities	8,687,225		278,236		1,591,254		142,045		10,278,479		420,281
Asset-backed securities	764,102		14,417		211,254		9,081		975,356		23,498
Residential mortgage-backed securities	3,679		63		10,029		823		13,708		886
Commercial mortgage-backed securities	838,617		24,039		280,386		19,177		1,119,003		43,216
Collateralized debt obligations	296,314		1,191		—		—		296,314		1,191
Total fixed maturities	$	11,580,133	$	345,827	$	2,278,938	$	179,995	$	13,859,071	$	525,822
Total number of securities in an unrealized loss position			1,076				268				1,344



	December 31, 2017
	Less than twelve months				Twelve months or longer				Total
	Estimated		Unrealized		Estimated		Unrealized		Estimated		Unrealized
Fixed maturities:	fair value		loss and OTTI		fair value		loss and OTTI		fair value		loss and OTTI
U.S. government direct obligations and U.S. agencies	$	755,861	$	4,159	$	230,447	$	3,724	$	986,308	$	7,883
Obligations of U.S. states and their subdivisions	24,908		180		37,012		1,475		61,920		1,655
Corporate debt securities	2,229,585		19,568		2,036,323		90,809		4,265,908		110,377
Asset-backed securities	544,778		3,011		245,341		7,120		790,119		10,131
Residential mortgage-backed securities	4,405		23		11,416		626		15,821		649
Commercial mortgage-backed securities	342,820		2,451		295,164		10,538		637,984		12,989
Collateralized debt obligations	7,277		80		—		—		7,277		80
Total fixed maturities	$	3,909,634	$	29,472	$	2,855,703	$	114,292	$	6,765,337	$	143,764
Total number of securities in an unrealized loss position			368				293				661

Other-than-temporary impairment recognition

The OTTI on fixed maturity securities where the loss portion is bifurcated and the credit related component is recognized in investment (losses) gains is summarized as follows:



	Three Months Ended June 30,						Six Months Ended June 30,
	2018			2017			2018			2017
Beginning balance	$	52,775		$	80,359		$	62,231		$	83,665
Reductions:
Due to sales, maturities or payoffs during the period	—			—			(1,510		)	—
Due to increases in cash flows expected to be collected that are recognized over the remaining life of the security	(3,092		)	(2,948		)	(11,038		)	(6,254		)
Ending balance	$	49,683		$	77,411		$	49,683		$	77,411

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

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