Derivative Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	$ 18,857		$ 19,429		$ 66,344		$ (47,097)
Futures on equity indices | Net investment income
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	222	[1]	(25)	[1]	312	[1]	61	[1]
Futures on equity indices | Realized investment gains (losses)
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	(72)	[2]	(330)	[2]	(431)	[2]	(1,442)	[2]
Interest rate swaps | Net investment income
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	467	[1]	(597)	[1]	2,517	[1]	(1,912)	[1]
Interest rate swaps | Realized investment gains (losses)
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	0	[2]	14	[2]	0	[2]	(622)	[2]
Interest rate futures | Net investment income
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	10	[1]	(143)	[1]	(55)	[1]	(663)	[1]
Interest rate futures | Realized investment gains (losses)
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	65	[2]	39	[2]	152	[2]	529	[2]
Interest rate swaptions | Net investment income
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	835	[1]	709	[1]	1,677	[1]	2,293	[1]
Interest rate swaptions | Realized investment gains (losses)
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	(917)	[2]	(735)	[2]	(2,627)	[2]	(2,043)	[2]
Other forward contracts | Net investment income
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	(16,147)	[1]	86,590	[1]	(2,087)	[1]	55,530	[1]
Other forward contracts | Realized investment gains (losses)
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	16,894	[2]	(66,093)	[2]	56,471	[2]	(98,828)	[2]
Cross-currency swaps | Net investment income
Derivatives not designated as hedging instruments
Gain (loss) on derivatives recognized in net income	17,500	[1]	0	[1]	10,415	[1]	0	[1]
Cash flow hedges
Effect of derivative instruments in the condensed consolidated statement of income
Gain (loss) recognized in OCI on derivatives (Effective portion)	7,408		(49,908)		11,302		(33,000)
Gain (loss) reclassified from OCI into net income (Effective portion)	2,639		591		7,224		4,539
Cash flow hedges | Interest rate swaps
Effect of derivative instruments in the condensed consolidated statement of income
Gain (loss) recognized in OCI on derivatives (Effective portion)	184		(991)		5,328		(10,792)
Cash flow hedges | Interest rate swaps | Net investment income
Effect of derivative instruments in the condensed consolidated statement of income
Gain (loss) reclassified from OCI into net income (Effective portion)	1,876		575	[1]	5,581		4,491	[1]
Cash flow hedges | Interest rate futures
Effect of derivative instruments in the condensed consolidated statement of income
Gain (loss) recognized in OCI on derivatives (Effective portion)	0		0		0		0
Cash flow hedges | Interest rate futures | Net investment income
Effect of derivative instruments in the condensed consolidated statement of income
Gain (loss) reclassified from OCI into net income (Effective portion)	17		16	[1]	52		48	[1]
Cash flow hedges | Cross-currency swaps
Effect of derivative instruments in the condensed consolidated statement of income
Gain (loss) recognized in OCI on derivatives (Effective portion)	7,224		(48,917)		5,974		(22,208)
Cash flow hedges | Cross-currency swaps | Net investment income
Effect of derivative instruments in the condensed consolidated statement of income
Gain (loss) reclassified from OCI into net income (Effective portion)	900		0	[1]	1,745		0	[1]
Cash flow hedges | Cross-currency swaps | Realized investment gains (losses)
Effect of derivative instruments in the condensed consolidated statement of income
Gain (loss) reclassified from OCI into net income (Effective portion)	(154)		0	[1]	(154)		0	[1]
Fair value hedges
Effect of derivative instruments in the condensed consolidated statement of income
Gain (loss) on derivatives recognized in net income	395	[3]	338	[3]	(2,005)	[4]	7,233	[4]
Gain (loss) on hedged assets recognized in net income	(406)	[3]	(338)	[3]	1,994	[4]	(7,233)	[4]
Hedge ineffectiveness	(11)		0		(11)		0
Fair value hedges | Interest rate swaps | Net investment income
Effect of derivative instruments in the condensed consolidated statement of income
Gain (loss) on derivatives recognized in net income	395		(1,756)		(2,005)		5,324	[1]
Gain (loss) on hedged assets recognized in net income	(406)		1,768	[1]	1,994		(4,290)	[1]
Fair value hedges | Interest rate swaps | Realized investment gains (losses)
Effect of derivative instruments in the condensed consolidated statement of income
Gain (loss) on derivatives recognized in net income	0		2,094	[2]	0		1,909	[2]
Gain (loss) on hedged assets recognized in net income	$ 0		$ (2,106)	[2]	$ 0		$ (2,943)	[2]

[1] Net investment income.

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

[3] Hedge ineffectiveness of ($11) and zero was recognized for the three months ended September 30, 2014 and 2013, respectively.

[4] Hedge ineffectiveness of ($11) and zero was recognized for the nine months ended September 30, 2014 and 2013, respectively