Derivative Instruments (Detail) - Gross amounts of derivative fair values contained in the consolidated balance sheet (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Credit Exposure [Member] | Financial Operations Derivatives [Member]
Asset derivative notional amount	$ 0	[1],[2]	$ 0	[1],[2]
Asset derivative fair value	0	[1],[2],[3]	0	[1],[2],[3]
Liability derivative fair value	(10,288)	[1],[2],[3]	(10,288)	[1],[2],[3]
Liability derivative notional amount	82,146	[1],[2]	81,678	[1],[2]
Investment Related Derivatives [Member] | Interest Rate Exposure [Member]
Asset derivative notional amount	92,377		70,978
Asset derivative fair value	2,311	[3]	1,946	[3]
Liability derivative fair value	(26)	[3]	(43)	[3]
Liability derivative notional amount	8,886		55,033
Investment Related Derivatives [Member] | Foreign Exchange Exposure [Member]
Asset derivative notional amount	78,100		232,422
Asset derivative fair value	384	[3]	3,759	[3]
Liability derivative fair value	(2,137)	[3]	(11,737)	[3]
Liability derivative notional amount	131,658		384,592
Investment Related Derivatives [Member] | Credit Exposure [Member]
Asset derivative notional amount	113,750		172,500
Asset derivative fair value	1,745	[3]	5,271	[3]
Liability derivative fair value	(14,839)	[3]	(13,986)	[3]
Liability derivative notional amount	486,513		449,513
Investment Related Derivatives [Member] | Financial Market Exposure [Member]
Asset derivative notional amount	49,088		23,874
Asset derivative fair value	1,392	[3]	615	[3]
Liability derivative fair value	0	[3]	0	[3]
Liability derivative notional amount	13,880		14,321
Other Non-Investment Derivatives [Member] | Guaranteed Minimum Income Benefit Contract [Member]
Asset derivative notional amount	0		0
Asset derivative fair value	0	[3]	0	[3]
Liability derivative fair value	(20,475)	[3]	(22,490)	[3]
Liability derivative notional amount	70,352		78,777
Other Non-Investment Derivatives [Member] | Modified Coinsurance Funds Withheld Contract [Member]
Asset derivative notional amount	76,890		77,200
Asset derivative fair value	0	[3]	0	[3]
Liability derivative fair value	0	[3]	0	[3]
Liability derivative notional amount	0		0
Other Non-Investment Derivatives [Member]
Asset derivative notional amount	410,205		576,974
Asset derivative fair value	5,832	[3]	11,591	[3]
Liability derivative fair value	(47,765)	[3]	(58,544)	[3]
Liability derivative notional amount	793,435		1,063,914
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Asset derivative notional amount	156,271	[1]	156,271	[1]
Asset derivative fair value	106,941	[1],[3]	109,761	[1],[3]
Liability derivative fair value	0	[1],[3]	0	[1],[3]
Liability derivative notional amount	0	[1]	0	[1]
Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Asset derivative notional amount	971,816		2,033,428
Asset derivative fair value	5,830	[3]	25,387	[3]
Liability derivative fair value	(21,415)	[3]	(4,518)	[3]
Liability derivative notional amount	1,798,665		457,892
Designated as Hedging Instrument [Member]
Asset derivative notional amount	1,128,087		2,189,699
Asset derivative fair value	112,771	[3]	135,148	[3]
Liability derivative fair value	(21,415)	[3]	(4,518)	[3]
Liability derivative notional amount	$ 1,798,665		$ 457,892

[1] At March 31, 2012 and December 31, 2011, the Company held net cash collateral related to these derivative positions of $77.5 million and $77.1 million, respectively. The collateral balance is included within cash and cash equivalents and the corresponding liability to return the collateral has been offset against the derivative asset within the balance sheet as appropriate under the netting agreement.

[2] Financial operations derivatives represent interests in variable interest entities as described in Note 10, "Variable Interest Entities."

[3] Derivative instruments in an asset or liability position are included within Other Assets or Other Liabilities, respectively, in the Balance Sheet.