Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Assets
Mortgage loans on real estate (net of valuation allowances)		$ 3,170,002	$ 2,712,238
Policy loans		1,444,009	1,284,284
Funds withheld at interest		5,675,174	5,922,561
Cash and cash equivalents		1,747,692	1,645,669	$ 1,118,745	$ 923,647
Short-term investments		58,200	97,694
Other invested assets		1,187,504	1,198,319
Accrued investment income		342,088	261,096
Liabilities
Interest-sensitive contract liabilities		13,699,896	12,591,497
Long-term debt		2,313,053	2,314,293
Collateral finance and securitization notes		914,452	782,701
Reported Value Measurement [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)		3,170,002	2,712,238
Policy loans		1,444,009	1,284,284
Funds withheld at interest	[1]	5,723,581	5,897,202
Cash and cash equivalents	[2]	925,508	745,823
Short-term investments	[2]	46,371	52,504
Other invested assets	[2]	381,970	465,720
Accrued investment income		342,088	261,096
Liabilities
Interest-sensitive contract liabilities	[1]	9,807,740	9,623,596
Long-term debt		2,313,053
Debt, Long-term and Short-term, Combined Amount			2,314,293
Collateral finance and securitization notes		914,452	782,701
Estimate of Fair Value Measurement [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)		3,255,198	2,803,942
Policy loans		1,444,009	1,284,284
Funds withheld at interest	[1]	6,089,263	6,367,165
Cash and cash equivalents	[2]	925,508	745,823
Short-term investments	[2]	46,371	52,504
Other invested assets	[2]	434,205	518,261
Accrued investment income		342,088	261,096
Liabilities
Interest-sensitive contract liabilities	[1]	10,139,341	9,666,240
Long-term Debt, Fair Value		2,451,987
Debt, Long-term and Short-term, Combined Amount			2,518,399
Collateral finance and securitization notes		809,943	674,984
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 1 Member
Assets
Mortgage loans on real estate (net of valuation allowances)		0	0
Policy loans		0	0
Funds withheld at interest	[1]	0	0
Cash and cash equivalents	[2]	925,508	745,823
Short-term investments	[2]	46,371	52,504
Other invested assets	[2]	4,563	4,674
Accrued investment income		0	0
Liabilities
Interest-sensitive contract liabilities	[1]	0	0
Long-term Debt, Fair Value		0
Debt, Long-term and Short-term, Combined Amount			0
Collateral finance and securitization notes		0	0
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 2 Member
Assets
Mortgage loans on real estate (net of valuation allowances)		0	0
Policy loans		1,444,009	1,284,284
Funds withheld at interest	[1]	0	0
Cash and cash equivalents	[2]	0	0
Short-term investments	[2]	0	0
Other invested assets	[2]	34,526	35,446
Accrued investment income		342,088	261,096
Liabilities
Interest-sensitive contract liabilities	[1]	0	0
Long-term Debt, Fair Value		0
Debt, Long-term and Short-term, Combined Amount			0
Collateral finance and securitization notes		0	0
Estimate of Fair Value Measurement [Member] | Fair Value Inputs Level 3 Member
Assets
Mortgage loans on real estate (net of valuation allowances)		3,255,198	2,803,942
Policy loans		0	0
Funds withheld at interest	[1]	6,089,263	6,367,165
Cash and cash equivalents	[2]	0	0
Short-term investments	[2]	0	0
Other invested assets	[2]	395,116	478,141
Accrued investment income		0	0
Liabilities
Interest-sensitive contract liabilities	[1]	10,139,341	9,666,240
Long-term Debt, Fair Value		2,451,987
Debt, Long-term and Short-term, Combined Amount			2,518,399
Collateral finance and securitization notes		$ 809,943	$ 674,984

[1] Carrying values presented herein differ from those presented in the condensed consolidated balance sheets because certain items within the respective financial statement caption are embedded derivatives and are measured at fair value on a recurring basis.

[2] Carrying values presented herein differ from those presented in the condensed consolidated balance sheets because certain items within the respective financial statement caption are measured at fair value on a recurring basis.