Fair Value of Financial Instruments (Assets and Liabilities Measured on Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	$ 2,826,001		$ 2,624,953
Derivatives, index options	57,890		30,844
Total assets	2,883,891		2,655,797
Policyholder account balances	72,470	[1]	47,129	[1]
Other liabilities	2,718	[2]	1,647	[2]
Total liabilities	75,188		48,776
Percent of total	100.00%
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0		0
Total assets	11,968		8,233
Policyholder account balances	0	[1]	0	[1]
Other liabilities	0	[2]	0	[2]
Total liabilities	0		0
Percent of total	0.40%
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	57,890		30,844
Total assets	2,871,923		2,639,446
Policyholder account balances	72,470	[1]	47,129	[1]
Other liabilities	0	[2]	0	[2]
Total liabilities	72,470		47,129
Percent of total	99.60%
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0		0
Total assets	0		8,118
Policyholder account balances	0	[1]	0	[1]
Other liabilities	2,718	[2]	1,647	[2]
Total liabilities	2,718		1,647
Percent of total	0.00%
Priced by Third-Party Vendors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	57,890
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
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	57,890
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	0
Priced Internally [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0
Priced Internally [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0
Priced Internally [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0
Priced Internally [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, index options	0
Debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	2,813,734		2,608,407
Debt securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0		0
Debt securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	2,813,734		2,608,407
Debt securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0		0
Debt securities [Member] | Priced by Third-Party Vendors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	2,813,734
Debt securities [Member] | Priced by Third-Party Vendors [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0
Debt securities [Member] | Priced by Third-Party Vendors [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	2,813,734
Debt securities [Member] | Priced by Third-Party Vendors [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0
Debt securities [Member] | Priced Internally [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0
Debt securities [Member] | Priced Internally [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0
Debt securities [Member] | Priced Internally [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0
Debt securities [Member] | Priced Internally [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	12,267		16,546
Equity Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	11,968		8,233
Equity Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	299		195
Equity Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0		8,118
Equity Securities [Member] | Priced by Third-Party Vendors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	12,267
Equity Securities [Member] | Priced by Third-Party Vendors [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	11,968
Equity Securities [Member] | Priced by Third-Party Vendors [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	299
Equity Securities [Member] | Priced by Third-Party Vendors [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0
Equity Securities [Member] | Priced Internally [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0
Equity Securities [Member] | Priced Internally [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0
Equity Securities [Member] | Priced Internally [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	0
Equity Securities [Member] | Priced Internally [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale	$ 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.