Derivative Instruments - Gross amounts of derivative fair values contained in the consolidated balance sheet (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Derivatives Fair Value [Line Items]
Asset derivative fair value	$ 136,659		$ 27,487
Liability derivative fair value	31,184		105,485
Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Asset derivative notional amount	2,300,609		1,005,610
Asset derivative fair value	121,862	[1]	26,098	[1]
Liability derivative notional amount	302,211		2,572,227
Liability derivative fair value	2,936	[1]	70,462	[1]
Designated as Hedging Instrument | Foreign Exchange Contract
Derivatives Fair Value [Line Items]
Asset derivative notional amount	2,300,609		1,005,610
Asset derivative fair value	121,862	[1]	26,098	[1]
Liability derivative notional amount	302,211		2,572,227
Liability derivative fair value	2,936	[1]	70,462	[1]
Not Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Asset derivative notional amount	592,791		172,800
Asset derivative fair value	14,797	[1]	1,389	[1]
Liability derivative notional amount	5,804,625		513,512
Liability derivative fair value	28,248	[1]	35,023	[1]
Not Designated as Hedging Instrument | Investment Related Derivatives | Interest Rate Contract
Derivatives Fair Value [Line Items]
Asset derivative notional amount	394,597		30,702
Asset derivative fair value	206	[1]	266	[1]
Liability derivative notional amount	20,782		10,259
Liability derivative fair value	51	[1]	8	[1]
Not Designated as Hedging Instrument | Investment Related Derivatives | Foreign Exchange Contract
Derivatives Fair Value [Line Items]
Asset derivative notional amount	7,385		17,497
Asset derivative fair value	403	[1]	12	[1]
Liability derivative notional amount	288,376		50,614
Liability derivative fair value	4,724	[1]	680	[1]
Not Designated as Hedging Instrument | Investment Related Derivatives | Credit Exposure
Derivatives Fair Value [Line Items]
Asset derivative notional amount	2,408		0
Asset derivative fair value	165	[1]	0	[1]
Liability derivative notional amount	14,270		340,020
Liability derivative fair value	9,836	[1]	15,128	[1]
Not Designated as Hedging Instrument | Investment Related Derivatives | Financial Market Exposure
Derivatives Fair Value [Line Items]
Asset derivative notional amount	46,145		58,232
Asset derivative fair value	360	[1]	1,111	[1]
Liability derivative notional amount	33,670		14,821
Liability derivative fair value	34	[1]	77	[1]
Not Designated as Hedging Instrument | Financial Operations Derivatives | Credit Exposure
Derivatives Fair Value [Line Items]
Asset derivative notional amount	0	[2]	0	[2]
Asset derivative fair value	0	[1],[2]	0	[1],[2]
Liability derivative notional amount	0	[2]	44,234	[2]
Liability derivative fair value	0	[1],[2]	4,190	[1],[2]
Not Designated as Hedging Instrument | Other Non Investment Derivatives | Other Credit Derivatives [Member]
Derivatives Fair Value [Line Items]
Asset derivative notional amount	31,060	[2]	0	[2]
Asset derivative fair value	60	[1],[2]	0	[1],[2]
Liability derivative notional amount	0	[2]	0	[2]
Liability derivative fair value	0	[1],[2]	0	[1],[2]
Not Designated as Hedging Instrument | Other Non Investment Derivatives | Guaranteed Minimum Income Benefit
Derivatives Fair Value [Line Items]
Asset derivative notional amount	46,249	[2]	0	[2]
Asset derivative fair value	13,603	[1],[2]	0	[1],[2]
Liability derivative notional amount	46,249	[2]	53,564	[2]
Liability derivative fair value	13,603	[1],[2]	14,940	[1],[2]
Not Designated as Hedging Instrument | Other Non Investment Derivatives | Modified Coinsurance Funds Withheld Contract
Derivatives Fair Value [Line Items]
Asset derivative notional amount	64,947	[2],[3]	66,369	[2],[3]
Asset derivative fair value	0	[1],[2],[3]	0	[1],[2],[3]
Liability derivative notional amount	5,401,278	[2]	0	[2],[3]
Liability derivative fair value	$ 0	[1],[2],[3]	$ 0	[1],[2],[3]

[1] Derivative instruments in an asset or liability position are included within Other assets or Other liabilities, respectively, in the balance sheets on a net basis where the Company has both a legal right of offset and the intention to settle the contracts on a net basis.

[2] Financial operations derivatives represent interests in variable interest entities as described in Note 18, “Variable Interest Entities".

[3] The fair value movements in derivative assets and liabilities relating to modified coinsurance funds withheld contracts are included within the associated asset or liability at each period end on the face of the balance sheets. Notional amounts associated with reinsurance agreements under which the Company assumes reinsurance risk are recorded as asset derivative notional amounts. Notional amounts associated with the Life Retro Arrangements under which the Company cedes reinsurance risk are recorded as liability derivative notional amounts. Included in the liability derivative notional amount at December 31, 2014 is the cumulative net realized and unrealized loss on life retrocession embedded derivative of $450.8 million.