Derivative Financial Instruments (Details 2) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income		$ 72,677	$ 124,086	$ (115,078)
Policyholders' Funds
Derivatives not designated as hedging instruments
Embedded derivatives - GLWB		11,257
Net investment income
Derivatives not designated as hedging instruments
Change in fair value		11,257
Futures on equity indices | Net investment income
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	[1]	(284)	(41)	(97)
Futures on equity indices | Realized investment gains (losses)
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	[2]	(527)	(534)	(3,396)
Interest rate swaps | Net investment income
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	[1]	(1,094)	6,508	(3,668)
Interest rate swaps | Realized investment gains (losses)
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	[2]	0	0	(622)
Interest rate futures | Net investment income
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	[1]	(65)	(51)	(458)
Interest rate futures | Realized investment gains (losses)
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	[2]	1	305	303
Interest rate swaptions | Net investment income
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	[1]	2,868	2,424	3,241
Interest rate swaptions | Realized investment gains (losses)
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	[2]	(3,115)	(3,578)	(2,828)
Other forward contracts | Realized investment gains (losses)
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	[2]	5,074	94,465	(57,442)
Cross-currency swaps | Net investment income
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	[1]	69,819	24,588	(50,111)
Cash flow hedges
Effect of derivative instruments in the consolidated statement of income
Gain (loss) recognized in OCI on derivatives (Effective portion)		31,061	20,137	3,102
Gain (loss) reclassified from OCI into net income (Effective portion)		12,380	8,408	5,130
Cash flow hedges | Interest rate swaps
Effect of derivative instruments in the consolidated statement of income
Gain (loss) recognized in OCI on derivatives (Effective portion)		2,228	9,096	(12,285)
Cash flow hedges | Interest rate swaps | Net investment income
Effect of derivative instruments in the consolidated statement of income
Gain (loss) reclassified from OCI into net income (Effective portion)	[1]	6,779	7,462	5,067
Cash flow hedges | Interest rate swaps | Realized investment gains (losses)
Effect of derivative instruments in the consolidated statement of income
Gain (loss) reclassified from OCI into net income (Effective portion)	[2]	3,634	0	0
Cash flow hedges | Interest rate futures | Net investment income
Effect of derivative instruments in the consolidated statement of income
Gain (loss) reclassified from OCI into net income (Effective portion)	[1]	(134)	70	63
Cash flow hedges | Cross-currency swaps
Effect of derivative instruments in the consolidated statement of income
Gain (loss) recognized in OCI on derivatives (Effective portion)		28,833	11,041	15,387
Cash flow hedges | Cross-currency swaps | Net investment income
Effect of derivative instruments in the consolidated statement of income
Gain (loss) reclassified from OCI into net income (Effective portion)	[1]	2,101	1,030	0
Cash flow hedges | Cross-currency swaps | Realized investment gains (losses)
Effect of derivative instruments in the consolidated statement of income
Gain (loss) reclassified from OCI into net income (Effective portion)	[2]	0	(154)	0
Fair value hedges
Effect of derivative instruments in the consolidated statement of income
Gain (loss) on derivatives recognized in net income		(734)	(3,444)	8,251
Gain (loss) on hedged assets recognized in net income		738	3,439	(8,251)
Fair value hedges | Interest rate swaps | Net investment income
Effect of derivative instruments in the consolidated statement of income
Gain (loss) on derivatives recognized in net income	[1]	(1,507)	(3,444)	6,342
Gain (loss) on hedged assets recognized in net income	[1]	1,511	3,439	(5,308)
Fair value hedges | Interest rate swaps | Realized investment gains (losses)
Effect of derivative instruments in the consolidated statement of income
Gain (loss) on derivatives recognized in net income	[2]	773	0	1,909
Gain (loss) on hedged assets recognized in net income	[2]	$ (773)	$ 0	$ (2,943)

[1] Net investment income.

[2] Represents realized gains (losses) on closed positions recorded in realized investment gains (losses), net.