Investments (Details 2) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost		$ 6,785,626	$ 6,375,237
Amortized Cost/Cost, Equity securities		95,722	99,904
Unrealized Gains		395,237	543,868
Unrealized Losses		89,523	26,015
Fair Value		7,091,340	6,893,090
Fair Value, Equity securities		99,797	110,655
OTTI in AOCI	[1]	(2,758)	2,879
Mortgage-backed securities [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost	[2]	461,862	484,561
Unrealized Gains	[2]	44,413	52,555
Unrealized Losses	[2]	1,861	1,390
Fair Value	[2]	504,414	535,726
OTTI in AOCI	[1],[2]	0	0
Other, including U.S. Treasury Securities [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost	[2]	532,373	512,596
Unrealized Gains	[2]	21,153	28,652
Unrealized Losses	[2]	7,415	3,049
Fair Value	[2]	546,111	538,199
OTTI in AOCI	[1],[2]	0	0
Municipal bonds [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost		1,553,603	1,462,717
Unrealized Gains		165,680	189,533
Unrealized Losses		10,340	4,428
Fair Value		1,708,943	1,647,822
OTTI in AOCI	[1]	(4,140)	0
Foreign government bonds [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost		67,441	52,552
Unrealized Gains		6,288	6,984
Unrealized Losses		112	0
Fair Value		73,617	59,536
OTTI in AOCI	[1]	0	0
Corporate bonds [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost		2,687,376	2,608,633
Unrealized Gains		140,873	237,372
Unrealized Losses		48,834	11,256
Fair Value		2,779,415	2,834,749
OTTI in AOCI	[1]	0	0
Other mortgage-backed securities [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost		1,482,971	1,254,178
Unrealized Gains		16,830	28,772
Unrealized Losses		20,961	5,892
Fair Value		1,478,840	1,277,058
OTTI in AOCI	[1]	1,382	2,879
Equity securities [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost, Equity securities	[3]	95,722	99,904
Unrealized Gains	[3]	8,405	14,159
Unrealized Losses	[3]	4,330	3,408
Fair Value, Equity securities	[3]	99,797	110,655
OTTI in AOCI	[1],[3]	$ 0	$ 0

[1] Related to securities for which an unrealized loss was bifurcated to distinguish the credit-related portion and the portion driven by other market factors. Represents the amount of other-than-temporary impairment losses in AOCI which was not included in earnings; amounts also include unrealized gains/(losses) on such impaired securities relating to changes in the fair value of those securities subsequent to the impairment measurement date.

[2] Fair value includes securities issued by Federal National Mortgage Association (“FNMA”) of $231,294 and $302,222; Federal Home Loan Mortgage Corporation (“FHLMC”) of $363,957 and $432,432; and Government National Mortgage Association (“GNMA”) of $130,940 and $137,867 as of December 31, 2015 and 2014, respectively.

[3] Includes nonredeemable (perpetual) preferred stocks, common stocks and closed-end funds.