Investments (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost	$ 6,187,429		$ 5,784,205
Amortized Cost/Cost, Equity securities	97,224		84,754
Unrealized Gains	523,683		344,286
Unrealized Losses	34,773		118,918
Fair Value	6,676,339		6,009,573
Fair Value, Equity securities	109,462		91,858
OTTI in AOCI	2,866	[1]	2,812	[1]
Mortgage-backed securities [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost	546,236	[2]	555,574	[2]
Unrealized Gains	45,587	[2]	33,711	[2]
Unrealized Losses	9,691	[2]	19,560	[2]
Fair Value	582,132	[2]	569,725	[2]
OTTI in AOCI	0	[1],[2]	0	[1],[2]
Other, including U.S. Treasury Securities [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost	464,978	[2]	449,060	[2]
Unrealized Gains	19,207	[2]	9,865	[2]
Unrealized Losses	8,007	[2]	23,351	[2]
Fair Value	476,178	[2]	435,574	[2]
OTTI in AOCI	0	[1],[2]	0	[1],[2]
Municipal bonds [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost	1,455,567		1,425,441
Unrealized Gains	149,837		80,701
Unrealized Losses	7,515		34,615
Fair Value	1,597,889		1,471,527
OTTI in AOCI	0	[1]	0	[1]
Foreign government bonds [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost	50,604		50,641
Unrealized Gains	6,435		4,700
Unrealized Losses	0		390
Fair Value	57,039		54,951
OTTI in AOCI	0	[1]	0	[1]
Corporate bonds [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost	2,599,455		2,457,727
Unrealized Gains	269,905		188,832
Unrealized Losses	5,623		32,150
Fair Value	2,863,737		2,614,409
OTTI in AOCI	0	[1]	0	[1]
Other mortgage-backed securities [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost	1,070,589		845,762
Unrealized Gains	32,712		26,477
Unrealized Losses	3,937		8,852
Fair Value	1,099,364		863,387
OTTI in AOCI	2,866	[1]	2,812	[1]
Equity securities [Member]
Unrealized gains and losses on fixed maturities and equity securities
Amortized Cost/Cost, Equity securities	97,224		84,754
Unrealized Gains	13,127		10,723
Unrealized Losses	889		3,619
Fair Value, Equity securities	109,462		91,858
OTTI in AOCI	$ 0	[1]	$ 0	[1]

[1] Represents the amount of other-than-temporary impairment losses in AOCI which, beginning April 1, 2009, was not included in earnings under current accounting guidance. Amounts also include unrealized gains/(losses) on impaired securities relating to changes in the fair value of such securities subsequent to the impairment measurement date.

[2] Fair value includes securities issued by Federal National Mortgage Association (“FNMA”) of $342,198 and $336,193; Federal Home Loan Mortgage Corporation (“FHLMC”) of $441,363 and $427,172; and Government National Mortgage Association (“GNMA”) of $136,208 and $126,245 as of June 30, 2014 and December 31, 2013, respectively.