Fair Value of Assets and Liabilities (Financial Instruments where Carrying Amounts and Fair Values May Differ) (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		$ 3,775,522	$ 3,129,951
Policy loans		1,427,602	1,468,796
Funds withheld at interest		5,875,919	5,880,203
Cash and cash equivalents		1,200,718	1,525,275	$ 1,645,669	$ 923,647
Short-term investments		76,710	558,284
Other invested assets		1,591,940	1,298,120
Accrued investment income		347,173	339,452
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities		14,029,354	13,663,873
Collateral finance and securitization notes		840,700	899,161
Carrying Value [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		3,775,522	3,129,951
Policy loans		1,427,602	1,468,796
Funds withheld at interest	[1]	5,893,381	5,956,380
Cash and cash equivalents	[2]	862,117	1,118,754
Short-term investments	[2]	32,469	27,511
Other invested assets	[2]	477,132	399,799
Accrued investment income		347,173	339,452
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	10,225,099	9,746,870
Long And Short Term Debt		3,088,635	2,297,548
Collateral finance and securitization notes		840,700	899,161
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		3,786,987	3,197,808
Policy loans		1,427,602	1,468,796
Funds withheld at interest	[1]	6,193,166	6,311,780
Cash and cash equivalents	[2]	862,117	1,118,754
Short-term investments	[2]	32,469	27,511
Other invested assets	[2]	510,640	444,342
Accrued investment income		347,173	339,452
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	10,234,544	9,841,576
Long And Short Term Debt		3,186,173	2,415,119
Collateral finance and securitization notes		745,805	791,275
Estimate of Fair Value Measurement [Member] | Net Asset Value [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		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]	296,773	293,599
Accrued investment income		0	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	0	0
Long And Short Term Debt		0	0
Collateral finance and securitization notes		0	0
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		0	0
Policy loans		0	0
Funds withheld at interest	[1]	0	0
Cash and cash equivalents	[2]	862,117	1,118,754
Short-term investments	[2]	32,469	27,511
Other invested assets	[2]	26,294	4,445
Accrued investment income		0	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	0	0
Long And Short Term Debt		0	0
Collateral finance and securitization notes		0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		0	0
Policy loans		1,427,602	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]	55,669	34,886
Accrued investment income		347,173	339,452
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	0	0
Long And Short Term Debt		0	0
Collateral finance and securitization notes		0	0
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Mortgage loans on real estate		3,786,987	3,197,808
Policy loans		0	0
Funds withheld at interest	[1]	6,193,166	6,311,780
Cash and cash equivalents	[2]	0	0
Short-term investments	[2]	0	0
Other invested assets	[2]	131,904	111,412
Accrued investment income		0	0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Interest-sensitive contract liabilities	[1]	10,234,544	9,841,576
Long And Short Term Debt		3,186,173	2,415,119
Collateral finance and securitization notes		$ 745,805	$ 791,275

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