Fair Value of Financial Instruments (Assets and Liabilities Measured on Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	$ 2,799,450		$ 2,651,544
Derivatives, index options	146,514		169,314
Total assets	2,945,964		2,820,858
Policyholder account balances	163,770	[1]	187,399	[1]
Other liabilities	7,658	[2]	5,939	[2]
Total liabilities	171,428		193,338
Percent of total	100.00%		100.00%
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	15,083		13,802
Derivatives, index options	0		0
Total assets	15,083		13,802
Policyholder account balances	0		0
Other liabilities	0		0
Total liabilities	0		0
Percent of total	0.50%		0.50%
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	2,784,367		2,637,742
Derivatives, index options	0		0
Total assets	2,784,367		2,637,742
Policyholder account balances			0
Other liabilities	0		0
Total liabilities	0		0
Percent of total	94.50%		93.50%
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Derivatives, index options	146,514		169,314
Total assets	146,514		169,314
Policyholder account balances	163,770		187,399
Other liabilities	7,658		5,939
Total liabilities	171,428		193,338
Percent of total	5.00%		6.00%
Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	2,782,949		2,636,666
Debt Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Debt Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	2,782,949		2,636,666
Debt Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	16,501		14,878
Equity Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	15,083		13,802
Equity Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	1,418		1,076
Equity Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Derivatives, Index Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	146,514		169,314
Derivatives, Index Options [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0		0
Derivatives, Index Options [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0		0
Derivatives, Index Options [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	146,514		169,314
Priced by Third-Party Vendors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	146,514		169,314
Priced by Third-Party Vendors [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0		0
Priced by Third-Party Vendors [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0		0
Priced by Third-Party Vendors [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	146,514		169,314
Priced by Third-Party Vendors [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	2,782,949		2,636,666
Priced by Third-Party Vendors [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Priced by Third-Party Vendors [Member] | Debt Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	2,782,949		2,636,666
Priced by Third-Party Vendors [Member] | Debt Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Priced by Third-Party Vendors [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	16,501		14,878
Priced by Third-Party Vendors [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	15,083		13,802
Priced by Third-Party Vendors [Member] | Equity Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	1,418		1,076
Priced by Third-Party Vendors [Member] | Equity Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Priced Internally [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0		0
Priced Internally [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0		0
Priced Internally [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0		0
Priced Internally [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0		0
Priced Internally [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Priced Internally [Member] | Debt Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Priced Internally [Member] | Debt Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Priced Internally [Member] | Debt Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Priced Internally [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Priced Internally [Member] | Equity Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Priced Internally [Member] | Equity Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	0		0
Priced Internally [Member] | Equity Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value (cost: $2,625,676 and $2,535,264)	$ 0		$ 0

[1] Represents the fair value of certain product-related embedded derivatives that were recorded at fair value.

[2] Represents the liability for share-based compensation.