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, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Assets
Mortgage loans on real estate (net of valuation allowances)		$ 3,607,700	$ 3,129,951
Policy loans		1,414,963	1,468,796
Funds withheld at interest		5,922,656	5,880,203
Cash and cash equivalents		1,379,693	1,525,275	$ 1,747,692	$ 1,645,669
Short-term investments		126,702	558,284
Other invested assets		1,777,065	1,298,120
Accrued investment income		391,837	339,452
Liabilities
Interest-sensitive contract liabilities		14,217,831	13,663,873
Short-term Debt		299,876	0
Long-term debt		2,788,834	2,297,548
Collateral finance and securitization notes		847,389	899,161
Reported Value Measurement [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)		3,607,700	3,129,951
Policy loans		1,414,963	1,468,796
Funds withheld at interest	[1]	5,958,025	5,956,380
Cash and cash equivalents	[2]	956,236	1,118,754
Short-term investments	[2]	34,551	27,511
Other invested assets	[2]	441,792	399,799
Accrued investment income		391,837	339,452
Liabilities
Interest-sensitive contract liabilities	[1]	10,258,427	9,746,870
Short-term Debt		299,876
Long-term debt		2,788,834
Debt, Long-term and Short-term, Combined Amount			2,297,548
Collateral finance and securitization notes		847,389	899,161
Estimate of Fair Value Measurement [Member]
Assets
Mortgage loans on real estate (net of valuation allowances)		3,787,558	3,197,808
Policy loans		1,414,963	1,468,796
Funds withheld at interest	[1]	6,417,638	6,311,780
Cash and cash equivalents	[2]	956,236	1,118,754
Short-term investments	[2]	34,551	27,511
Other invested assets	[2]	470,669	444,342
Accrued investment income		391,837	339,452
Liabilities
Interest-sensitive contract liabilities	[1]	10,711,363	9,841,576
Short-term Debt, Fair Value		305,181
Long-term Debt, Fair Value		2,986,195
Debt, Long-term and Short-term, Combined Amount			2,415,119
Collateral finance and securitization notes		752,494	791,275
Estimate of Fair Value Measurement [Member] | Net Asset Value [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]	0	0
Short-term investments	[2]	0	0
Other invested assets	[2]	285,671	293,599
Accrued investment income		0	0
Liabilities
Interest-sensitive contract liabilities	[1]	0	0
Short-term Debt, Fair Value		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 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]	956,236	1,118,754
Short-term investments	[2]	34,551	27,511
Other invested assets	[2]	13,932	4,445
Accrued investment income		0	0
Liabilities
Interest-sensitive contract liabilities	[1]	0	0
Short-term Debt, Fair Value		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		1,414,963	1,468,796
Funds withheld at interest	[1]	0	0
Cash and cash equivalents	[2]	0	0
Short-term investments	[2]	0	0
Other invested assets	[2]	51,765	34,886
Accrued investment income		391,837	339,452
Liabilities
Interest-sensitive contract liabilities	[1]	0	0
Short-term Debt, Fair Value		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)		3,787,558	3,197,808
Policy loans		0	0
Funds withheld at interest	[1]	6,417,638	6,311,780
Cash and cash equivalents	[2]	0	0
Short-term investments	[2]	0	0
Other invested assets	[2]	119,301	111,412
Accrued investment income		0	0
Liabilities
Interest-sensitive contract liabilities	[1]	10,711,363	9,841,576
Short-term Debt, Fair Value		305,181
Long-term Debt, Fair Value		2,986,195
Debt, Long-term and Short-term, Combined Amount			2,415,119
Collateral finance and securitization notes		$ 752,494	$ 791,275

[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.