Derivative Financial Instruments (Details 2) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income		$ 77,060	$ 72,677	$ 124,086
Interest rate swaps | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[1]	(4,541)	(1,094)	6,508
Cross-currency swaps | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[1]	85,746	69,819	24,588
Cross-currency swaps | Realized investment gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[1]	(1,601)
Interest rate futures | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[1]	(57)	(65)	(51)
Interest rate futures | Realized investment gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[2]	(164)	1	305
Futures on equity indices | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[1]	817	(284)	(41)
Futures on equity indices | Realized investment gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[2]	(7,930)	(527)	(534)
Interest rate swaptions | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[1]	302	2,868	2,424
Interest rate swaptions | Realized investment gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[2]	(313)	(3,115)	(3,578)
Currency forwards | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[2]	111
Other forward contracts | Realized investment gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[2]	4,690	5,074	94,465
Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in OCI on derivatives (Effective portion)		44,776	31,061	20,137
Gain (loss) reclassified from OCI into net income (Effective portion)		11,249	12,380	8,408
Cash flow hedges | Interest rate swaps | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in OCI on derivatives (Effective portion)		810	2,228	9,096
Gain (loss) reclassified from OCI into net income (Effective portion)	[1]	5,437	6,779	7,462
Cash flow hedges | Interest rate swaps | Realized investment gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) reclassified from OCI into net income (Effective portion)	[2]	0	3,634	0
Cash flow hedges | Interest rate swaps | Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in OCI on derivatives (Effective portion)		21,228
Gain (loss) reclassified from OCI into net income (Effective portion)	[2]	(2,657)
Cash flow hedges | Cross-currency swaps | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in OCI on derivatives (Effective portion)		22,738	28,833	11,041
Gain (loss) reclassified from OCI into net income (Effective portion)	[1]	8,469	2,101	1,030
Cash flow hedges | Cross-currency swaps | Realized investment gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) reclassified from OCI into net income (Effective portion)	[2]	0	0	(154)
Cash flow hedges | Interest rate futures | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) reclassified from OCI into net income (Effective portion)	[1]	0	(134)	70
Fair value hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income		0	(734)	(3,444)
Gain (loss) on hedged assets recognized in net income		0	738	3,439
Fair value hedges | Interest rate swaps | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[1]	0	(1,507)	(3,444)
Gain (loss) on hedged assets recognized in net income	[1]	0	1,511	3,439
Fair value hedges | Interest rate swaps | Realized investment gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives recognized in net income	[2]	0	773	0
Gain (loss) on hedged assets recognized in net income	[2]	$ 0	$ (773)	$ 0

[1] Net investment income.

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