Summary of Investments (Tables)

6 Months Ended

Jun. 30, 2016

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, 2016
	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	$	1,090,483	$	90,927	$	120	$	1,181,290	$	—
Obligations of U.S. states and their subdivisions	1,929,763		344,059		181		2,273,641		—
Foreign government securities	2,209		—		4		2,205		—
Corporate debt securities (2)	13,095,232		895,019		182,534		13,807,717		(1,672		)
Asset-backed securities	1,562,617		130,135		12,691		1,680,061		(79,080		)
Residential mortgage-backed securities	93,222		3,526		590		96,158		(26		)
Commercial mortgage-backed securities	1,036,035		56,508		1,740		1,090,803		—
Collateralized debt obligations	38,669		98		54		38,713		—
Total fixed maturities	$	18,848,230	$	1,520,272	$	197,914	$	20,170,588	$	(80,778	)

⁽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 $135,187 and estimated fair value of $97,019.

	December 31, 2015
	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	$	3,291,167	$	55,193	$	4,608	$	3,341,752	$	—
Obligations of U.S. states and their subdivisions	1,988,214		238,862		7,903		2,219,173		50
Foreign government securities	2,291		—		5		2,286		—
Corporate debt securities (2)	12,388,886		437,207		320,381		12,505,712		(1,810		)
Asset-backed securities	1,196,326		128,406		13,362		1,311,370		(86,474		)
Residential mortgage-backed securities	122,146		4,734		1,508		125,372		(123		)
Commercial mortgage-backed securities	1,009,320		19,117		11,529		1,016,908		—
Collateralized debt obligations	9,112		—		58		9,054		—
Total fixed maturities	$	20,007,462	$	883,519	$	359,354	$	20,531,627	$	(88,357	)

⁽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 $149,062 and estimated fair value of $116,423.

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, based on estimated cash flows, 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, 2016
	Amortized cost		Estimated fair value
Maturing in one year or less	$	628,975	$	655,798
Maturing after one year through five years	3,832,723		4,104,021
Maturing after five years through ten years	5,867,161		6,263,431
Maturing after ten years	5,059,694		5,478,203
Mortgage-backed and asset-backed securities	3,459,677		3,669,135
Total fixed maturities	$	18,848,230	$	20,170,588

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,
	2016		2015		2016		2015
Proceeds from sales	$	1,673,307	$	337,206	$	3,356,200	$	2,995,877
Gross realized gains from sales	26,810		8,584		46,667		31,935
Gross realized losses from sales	135		304		146		324

Schedule of the carrying value of the mortgage loan portfolio by component

The following table summarizes the carrying value of the mortgage loan portfolio by component:  

	June 30, 2016			December 31, 2015
Principal	$	3,491,994		$	3,242,627
Unamortized premium (discount) and fees, net	6,725			7,967
Mortgage provision allowance	(2,882		)	(2,890		)
Total mortgage loans	$	3,495,837		$	3,247,704

Financing Receivable Credit Quality Indicators

The following table summarizes the recorded investment of the mortgage loan portfolio by risk assessment category as of June 30, 2016, and December 31, 2015, respectively. 

	June 30, 2016		December 31, 2015
Performing	$	3,497,254	$	3,249,129
Non-performing	1,465		1,465
Total	$	3,498,719	$	3,250,594

Summary of activity in the mortgage provision allowance

The following table summarizes activity in the mortgage provision allowance:

	Six Months Ended June 30, 2016			Year Ended December 31, 2015
	Commercial mortgages			Commercial mortgages
Beginning balance	$	2,890		$	2,890
Provision increases	536			—
Provision decreases	(544		)	—
Ending balance	$	2,882		$	2,890
Allowance ending balance by basis of impairment method:
Individually evaluated for impairment	$	536		$	—
Collectively evaluated for impairment	2,346			2,890
Recorded investment balance in the mortgage loan portfolio, gross of allowance, by basis of impairment method:	$	3,498,719		$	3,250,594
Individually evaluated for impairment	13,805			14,031
Collectively evaluated for impairment	3,484,914			3,236,563

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, 2016
	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	$	1,373	$	10	$	11,755	$	110	$	13,128	$	120
Obligations of U.S. states and their subdivisions	632		87		10,101		94		10,733		181
Foreign government securities	2,205		4		—		—		2,205		4
Corporate debt securities	918,217		44,939		975,449		137,595		1,893,666		182,534
Asset-backed securities	199,178		4,215		213,912		8,476		413,090		12,691
Residential mortgage-backed securities	796		2		17,110		588		17,906		590
Commercial mortgage-backed securities	62,458		440		48,887		1,300		111,345		1,740
Collateralized debt obligations	9,944		54		—		—		9,944		54
Total fixed maturities	$	1,194,803	$	49,751	$	1,277,214	$	148,163	$	2,472,017	$	197,914
Total number of securities in an unrealized loss position			98				143				241

	December 31, 2015
	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	$	1,357,822	$	4,101	$	23,604	$	507	$	1,381,426	$	4,608
Obligations of U.S. states and their subdivisions	267,581		7,903		—		—		267,581		7,903
Foreign government securities	2,286		5		—		—		2,286		5
Corporate debt securities	4,412,965		202,874		552,791		117,507		4,965,756		320,381
Asset-backed securities	247,082		4,372		182,404		8,990		429,486		13,362
Residential mortgage-backed securities	—		—		18,625		1,508		18,625		1,508
Commercial mortgage-backed securities	429,175		11,154		44,498		375		473,673		11,529
Collateralized debt obligations	9,054		58		—		—		9,054		58
Total fixed maturities	$	6,725,965	$	230,467	$	821,922	$	128,887	$	7,547,887	$	359,354
Total number of securities in an unrealized loss position			558				106				664

Other than Temporary Impairment, Credit Losses Recognized in Earnings

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

	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Beginning balance	$	98,416		$	115,653		$	102,343		$	119,532
Initial impairments - credit loss on securities not previously impaired	—			—			—			450
Reductions due to increases in cash flows expected to be collected that are recognized over the remaining life of the security	(3,729		)	(8,740		)	(7,656		)	(13,069		)
Ending balance	$	94,687		$	106,913		$	94,687		$	106,913