Investments (Tables)

6 Months Ended

Jun. 30, 2017

Investments, Debt and Equity Securities [Abstract]

Available-For-Sale Investments

The following tables summarize the Company's available-for-sale investments. Commercial and residential mortgage-backed securities include securities issued by U.S. government-sponsored enterprises and U.S. government agencies.

	June 30, 2017
(dollars in thousands)	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Unrealized Other-Than- Temporary Impairment Losses		Estimated Fair Value
Fixed maturities:
U.S. Treasury securities	$	138,404	$	81	$	(844	)	$	—	$	137,641
U.S. government-sponsored enterprises	372,560		10,745		(1,426		)	—		381,879
Obligations of states, municipalities and political subdivisions	4,477,463		196,535		(20,632		)	—		4,653,366
Foreign governments	1,310,376		143,572		(2,231		)	—		1,451,717
Commercial mortgage-backed securities	1,188,439		8,014		(13,054		)	—		1,183,399
Residential mortgage-backed securities	830,679		21,786		(3,690		)	—		848,775
Asset-backed securities	37,856		25		(84		)	—		37,797
Corporate bonds	1,313,879		48,340		(3,301		)	—		1,358,918
Total fixed maturities	9,669,656		429,098		(45,262		)	—		10,053,492
Equity securities:
Insurance, banks and other financial institutions	888,805		976,110		(586		)	—		1,864,329
Industrial, consumer and all other	1,764,205		1,721,110		(8,817		)	—		3,476,498
Total equity securities	2,653,010		2,697,220		(9,403		)	—		5,340,827
Short-term investments	1,704,359		67		(10		)	—		1,704,416
Investments, available-for-sale	$	14,027,025	$	3,126,385	$	(54,675	)	$	—	$	17,098,735

	December 31, 2016
(dollars in thousands)	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Unrealized Other-Than- Temporary Impairment Losses			Estimated Fair Value
Fixed maturities:
U.S. Treasury securities	$	259,379	$	99	$	(894	)	$	—		$	258,584
U.S. government-sponsored enterprises	418,457		9,083		(4,328		)	—			423,212
Obligations of states, municipalities and political subdivisions	4,324,332		145,678		(41,805		)	—			4,428,205
Foreign governments	1,306,324		159,291		(2,153		)	—			1,463,462
Commercial mortgage-backed securities	1,055,947		3,953		(19,544		)	—			1,040,356
Residential mortgage-backed securities	779,503		18,749		(5,048		)	(2,258		)	790,946
Asset-backed securities	27,494		2		(158		)	—			27,338
Corporate bonds	1,420,298		49,146		(9,364		)	(673		)	1,459,407
Total fixed maturities	9,591,734		386,001		(83,294		)	(2,931		)	9,891,510
Equity securities:
Insurance, banks and other financial institutions	846,343		857,063		(5,596		)	—			1,697,810
Industrial, consumer and all other	1,635,105		1,421,080		(8,154		)	—			3,048,031
Total equity securities	2,481,448		2,278,143		(13,750		)	—			4,745,841
Short-term investments	2,336,100		57		(6		)	—			2,336,151
Investments, available-for-sale	$	14,409,282	$	2,664,201	$	(97,050	)	$	(2,931	)	$	16,973,502

Summary Of Gross Unrealized Investment Losses By Length Of Time That Securities Have Continuously Been In An Unrealized Loss Position

The following tables summarize gross unrealized investment losses by the length of time that securities have continuously been in an unrealized loss position.

	June 30, 2017
	Less than 12 months					12 months or longer					Total
(dollars in thousands)	Estimated Fair Value		Gross Unrealized Holding and Other-Than- Temporary Impairment Losses			Estimated Fair Value		Gross Unrealized Holding and Other-Than- Temporary Impairment Losses			Estimated Fair Value		Gross Unrealized Holding and Other-Than- Temporary Impairment Losses
Fixed maturities:
U.S. Treasury securities	$	95,984	$	(741	)	$	7,427	$	(103	)	$	103,411	$	(844	)
U.S. government-sponsored enterprises	137,702		(1,426		)	—		—			137,702		(1,426		)
Obligations of states, municipalities and political subdivisions	706,155		(17,574		)	31,626		(3,058		)	737,781		(20,632		)
Foreign governments	122,855		(2,231		)	—		—			122,855		(2,231		)
Commercial mortgage-backed securities	536,397		(12,801		)	14,693		(253		)	551,090		(13,054		)
Residential mortgage-backed securities	123,791		(1,806		)	74,672		(1,884		)	198,463		(3,690		)
Asset-backed securities	22,992		(51		)	5,106		(33		)	28,098		(84		)
Corporate bonds	378,552		(2,351		)	74,071		(950		)	452,623		(3,301		)
Total fixed maturities	2,124,428		(38,981		)	207,595		(6,281		)	2,332,023		(45,262		)
Equity securities:
Insurance, banks and other financial institutions	955		(60		)	1,375		(526		)	2,330		(586		)
Industrial, consumer and all other	88,643		(5,877		)	9,288		(2,940		)	97,931		(8,817		)
Total equity securities	89,598		(5,937		)	10,663		(3,466		)	100,261		(9,403		)
Short-term investments	56,385		(10		)	—		—			56,385		(10		)
Total	$	2,270,411	$	(44,928	)	$	218,258	$	(9,747	)	$	2,488,669	$	(54,675	)

	December 31, 2016
	Less than 12 months					12 months or longer					Total
(dollars in thousands)	Estimated Fair Value		Gross Unrealized Holding and Other-Than- Temporary Impairment Losses			Estimated Fair Value		Gross Unrealized Holding and Other-Than- Temporary Impairment Losses			Estimated Fair Value		Gross Unrealized Holding and Other-Than- Temporary Impairment Losses
Fixed maturities:
U.S. Treasury securities	$	122,950	$	(894	)	$	—	$	—		$	122,950	$	(894	)
U.S. government-sponsored enterprises	220,333		(4,324		)	7,618		(4		)	227,951		(4,328		)
Obligations of states, municipalities and political subdivisions	1,004,947		(37,685		)	31,723		(4,120		)	1,036,670		(41,805		)
Foreign governments	68,887		(2,145		)	5,005		(8		)	73,892		(2,153		)
Commercial mortgage-backed securities	749,889		(19,091		)	29,988		(453		)	779,877		(19,544		)
Residential mortgage-backed securities	181,557		(4,987		)	79,936		(2,319		)	261,493		(7,306		)
Asset-backed securities	14,501		(106		)	5,869		(52		)	20,370		(158		)
Corporate bonds	494,573		(8,357		)	93,790		(1,680		)	588,363		(10,037		)
Total fixed maturities	2,857,637		(77,589		)	253,929		(8,636		)	3,111,566		(86,225		)
Equity securities:
Insurance, banks and other financial institutions	8,808		(410		)	37,973		(5,186		)	46,781		(5,596		)
Industrial, consumer and all other	98,406		(4,772		)	29,650		(3,382		)	128,056		(8,154		)
Total equity securities	107,214		(5,182		)	67,623		(8,568		)	174,837		(13,750		)
Short-term investments	504,211		(6		)	—		—			504,211		(6		)
Total	$	3,469,062	$	(82,777	)	$	321,552	$	(17,204	)	$	3,790,614	$	(99,981	)

Schedule Of Amortized Cost And Estimated Fair Value Of Fixed Maturity Securities By Contractual Maturity Date

The amortized cost and estimated fair value of fixed maturities at June 30, 2017 are shown below by contractual maturity.

(dollars in thousands)	Amortized Cost		Estimated Fair Value
Due in one year or less	$	455,586	$	457,635
Due after one year through five years	1,224,123		1,267,114
Due after five years through ten years	1,568,950		1,645,516
Due after ten years	4,364,023		4,613,256
	7,612,682		7,983,521
Commercial mortgage-backed securities	1,188,439		1,183,399
Residential mortgage-backed securities	830,679		848,775
Asset-backed securities	37,856		37,797
Total fixed maturities	$	9,669,656	$	10,053,492

Components Of Net Investment Income

The following table presents the components of net investment income.

	Quarter Ended June 30,						Six Months Ended June 30,
(dollars in thousands)	2017			2016			2017			2016
Interest:
Municipal bonds (tax-exempt)	$	22,758		$	22,563		$	45,130		$	44,485
Municipal bonds (taxable)	17,793			16,222			35,298			32,110
Other taxable bonds	36,296			36,959			71,184			72,278
Short-term investments, including overnight deposits	5,834			2,654			10,783			4,945
Dividends on equity securities	19,017			16,758			39,623			34,410
Income from equity method investments	1,802			3,921			6,395			3,668
Other	24			190			(205		)	2,674
	103,524			99,267			208,208			194,570
Investment expenses	(4,225		)	(4,271		)	(8,541		)	(8,280		)
Net investment income	$	99,299		$	94,996		$	199,667		$	186,290

Summary Of Net Realized Investment Gains And The Change In Net Unrealized Gains On Investments

The following table presents net realized investment gains and the change in net unrealized gains on investments. 

	Quarter Ended June 30,						Six Months Ended June 30,
(dollars in thousands)	2017			2016			2017			2016
Realized gains:
Sales of fixed maturities	$	554		$	699		$	757		$	967
Sales of equity securities	1,295			17,798			16,533			45,526
Other	4,259			353			4,826			773
Total realized gains	6,108			18,850			22,116			47,266
Realized losses:
Sales of fixed maturities	(412		)	(142		)	(602		)	(555		)
Sales of equity securities	(786		)	(1,780		)	(1,216		)	(2,498		)
Other-than-temporary impairments	(604		)	(3,675		)	(3,817		)	(12,080		)
Other	(81		)	(718		)	(286		)	(2,996		)
Total realized losses	(1,883		)	(6,315		)	(5,921		)	(18,129		)
Gains on securities measured at fair value through net income	13,402			4,706			22,297			9,283
Net realized investment gains	$	17,627		$	17,241		$	38,492		$	38,420
Change in net unrealized gains on investments included in other comprehensive income:
Fixed maturities	$	79,413		$	213,026		$	84,060		$	452,982
Equity securities	204,372			42,786			423,424			139,744
Short-term investments	133			32			6			(35		)
Net increase	$	283,918		$	255,844		$	507,490		$	592,691