Fair Values of Financial Instruments Assets and Liabilities Measured on a Recurring Basis by Fair Value Hierarchy (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Assets
Derivative instruments	$ 577,784	$ 273,314
Fair Value, Measurements, Recurring [Member]
Assets
Assets, Fair Value Disclosure	25,490,586	19,250,813
Liabilities
Liabilities, Fair Value Disclosure	3,311,121	2,576,089
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and Cash Equivalents, at Carrying Value	2,397,434	404,952
Liabilities
Interest Rate Derivative Liabilities, at Fair Value	4,319
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Equity Securities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	61,604	62,845
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| US Treasury Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	5,205	4,678
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Corporate Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	13,242,999	10,116,361
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| US Government Corporations and Agencies Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	1,958,737	1,799,779
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	3,571,462	3,333,383
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Foreign Government Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	98,825	43,228
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Residential Mortgage Backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	2,565,959	2,703,290
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Commercial Mortgage Backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	78,912
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Asset-backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	888,393	463,390
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Assets
Cash and Cash Equivalents, at Carrying Value	2,397,434	404,952
Assets, Fair Value Disclosure	2,485,922	513,056
Liabilities
Interest Rate Derivative Liabilities, at Fair Value	0
Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Equity Securities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	44,851	44,229
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| US Treasury Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	5,205	4,678
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Corporate Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	38,049	58,827
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| US Government Corporations and Agencies Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Foreign Government Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Residential Mortgage Backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Commercial Mortgage Backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Asset-backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	383	370
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Assets
Cash and Cash Equivalents, at Carrying Value	0	0
Assets, Fair Value Disclosure	23,002,792	18,735,659
Liabilities
Interest Rate Derivative Liabilities, at Fair Value	4,319
Liabilities, Fair Value Disclosure	44,339	45,593
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Equity Securities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	16,753	18,616
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| US Treasury Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Corporate Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	13,204,950	10,057,534
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| US Government Corporations and Agencies Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	1,958,737	1,799,779
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	3,571,462	3,333,383
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Foreign Government Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	98,825	43,228
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Residential Mortgage Backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	2,564,087	2,701,192
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Commercial Mortgage Backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	78,912
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Asset-backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	888,010	463,020
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets
Cash and Cash Equivalents, at Carrying Value	0	0
Assets, Fair Value Disclosure	1,872	2,098
Liabilities
Interest Rate Derivative Liabilities, at Fair Value	0
Liabilities, Fair Value Disclosure	3,266,782	2,530,496
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Equity Securities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| US Treasury Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Corporate Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| US Government Corporations and Agencies Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Foreign Government Debt Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Residential Mortgage Backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	1,872	2,098
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Commercial Mortgage Backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Asset-backed Securities [Member] \| Fixed Maturities [Member]
Assets
Available-for-sale Securities, Fair Value Disclosure	0	0
Call Option [Member]
Assets
Derivative instruments	577,784	273,314
Call Option [Member] \| Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Derivative instruments	577,784	273,314
Call Option [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Assets
Derivative instruments	0	0
Call Option [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Assets
Derivative instruments	577,784	273,314
Call Option [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets
Derivative instruments	0	0
Interest Rate Swap [Member] \| Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Derivative Asset, Fair Value, Gross Asset	3,252
Interest Rate Swap [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Assets
Derivative Asset, Fair Value, Gross Asset	0
Interest Rate Swap [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Assets
Derivative Asset, Fair Value, Gross Asset	3,252
Interest Rate Swap [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets
Derivative Asset, Fair Value, Gross Asset	0
Option on Securities [Member]
Assets
Derivative instruments	40,020	45,593
Option on Securities [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Derivative instruments	40,020	45,593
Option on Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Assets
Derivative instruments	0	0
Option on Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Assets
Derivative instruments	40,020	45,593
Option on Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets
Derivative instruments	0	0
2015 Notes Embedded Conversion Derivative [Member]
Liabilities
Embedded Derivative, Fair Value of Embedded Derivative Liability	40,020	45,593
2015 Notes Embedded Conversion Derivative [Member] \| Fair Value, Measurements, Recurring [Member]
Liabilities
Fair Value Liabilities Measured on Recurring Basis, 2015 Notes Embedded Derivative	40,020	45,593
2015 Notes Embedded Conversion Derivative [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Liabilities
Fair Value Liabilities Measured on Recurring Basis, 2015 Notes Embedded Derivative	0	0
2015 Notes Embedded Conversion Derivative [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Liabilities
Fair Value Liabilities Measured on Recurring Basis, 2015 Notes Embedded Derivative	40,020	45,593
2015 Notes Embedded Conversion Derivative [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Liabilities
Fair Value Liabilities Measured on Recurring Basis, 2015 Notes Embedded Derivative	0	0
Fixed Index Annuity Embedded Derivative Financial Instruments [Member] \| Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Liabilities
Fair Value Liability Measured on Recurring Basis, Fixed Index Annuities Embedded Derivative	3,266,782	2,530,496
Fixed Index Annuity Embedded Derivative Financial Instruments [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Liabilities
Fair Value Liability Measured on Recurring Basis, Fixed Index Annuities Embedded Derivative	0	0
Fixed Index Annuity Embedded Derivative Financial Instruments [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Liabilities
Fair Value Liability Measured on Recurring Basis, Fixed Index Annuities Embedded Derivative	0	0
Fixed Index Annuity Embedded Derivative Financial Instruments [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Liabilities
Fair Value Liability Measured on Recurring Basis, Fixed Index Annuities Embedded Derivative	$ 3,266,782	$ 2,530,496