Derivative Instruments (Detail) - Gross amounts of derivative fair values contained in the consolidated balance sheet (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011		Dec. 31, 2010
Investment Related Derivatives [Member]
Derivatives not designated as hedging instruments:
Interest rate exposure	$ 89	[1]	$ 281	[1]
Interest rate exposure	(21)	[1]		[1]
Foreign exchange exposure	2,687	[1]	1,377	[1]
Foreign exchange exposure	(5,692)	[1]	(6,329)	[1]
Credit exposure	1,036	[1]	8,143	[1]
Credit exposure	(9,106)	[1]	(5,295)	[1]
Financial market exposure	410	[1]	705	[1]
Financial market exposure		[1]	(27)	[1]
Investment Related Derivatives [Member] | Other Assets Notional [Member]
Derivatives not designated as hedging instruments:
Interest rate exposure	132,584		117,689
Foreign exchange exposure	204,023		82,395
Credit exposure	92,500		128,450
Financial market exposure	134,596		135,912
Commodity futures	3,912
Investment Related Derivatives [Member] | Other Liabilities Notional [Member]
Derivatives not designated as hedging instruments:
Interest rate exposure	9,114		41,063
Foreign exchange exposure	441,898		272,724
Credit exposure	539,513		532,000
Financial market exposure	12,669		4,575
Financial Operations Derivatives [Member]
Derivatives not designated as hedging instruments:
Credit exposure		[1],[2],[3]		[1],[2],[3]
Credit exposure	(25,887)	[1],[2],[3]	(25,887)	[1],[2],[3]
Financial Operations Derivatives [Member] | Other Assets Notional [Member]
Derivatives not designated as hedging instruments:
Credit exposure		[2],[3]		[2],[3]
Financial Operations Derivatives [Member] | Other Liabilities Notional [Member]
Derivatives not designated as hedging instruments:
Credit exposure	175,231	[2],[3]	246,292	[2],[3]
Other Non Investment Derivatives [Member]
Derivatives not designated as hedging instruments:
Contingent capital facility		[1]
Contingent capital facility		[1]
Guaranteed minimum income benefit contract		[1]		[1]
Guaranteed minimum income benefit contract	(20,011)	[1]	(21,190)	[1]
Modified coinsurance funds withheld contract		[1]
Modified coinsurance funds withheld contract		[1]
Other Non Investment Derivatives [Member] | Other Assets Notional [Member]
Derivatives not designated as hedging instruments:
Contingent capital facility	350,000		350,000
Other Non Investment Derivatives [Member] | Other Liabilities Notional [Member]
Derivatives not designated as hedging instruments:
Guaranteed minimum income benefit contract	71,431		80,025
Modified coinsurance funds withheld contract	68,705		72,509
Not Designated as Hedging Instrument [Member]
Derivatives designated as hedging instruments:
Total derivatives as hedging instruments	4,222	[1]	10,506	[1]
Total derivatives as hedging instruments	(60,717)	[1]	(58,728)	[1]
Not Designated as Hedging Instrument [Member] | Other Assets Notional [Member]
Derivatives designated as hedging instruments:
Total derivatives as hedging instruments	917,615		814,446
Not Designated as Hedging Instrument [Member] | Other Liabilities Notional [Member]
Derivatives designated as hedging instruments:
Total derivatives as hedging instruments	1,318,561		1,249,188
Designated as Hedging Instrument [Member]
Derivatives designated as hedging instruments:
Total derivatives as hedging instruments	103,577	[1]	117,594	[1]
Total derivatives as hedging instruments	(27,259)	[1]	(12,161)	[1]
Designated as Hedging Instrument [Member] | Other Assets Notional [Member]
Derivatives designated as hedging instruments:
Total derivatives as hedging instruments	1,849,336		2,011,120
Designated as Hedging Instrument [Member] | Other Liabilities Notional [Member]
Derivatives designated as hedging instruments:
Total derivatives as hedging instruments	688,629		244,731
Other Assets Notional [Member] | Interest Rate Contract [Member]
Derivatives designated as hedging instruments:
Interest rate contracts (2)	159,056	[2]	161,028	[2]
Other Assets Notional [Member] | Foreign Exchange Contract [Member]
Derivatives designated as hedging instruments:
Foreign exchange contracts	1,690,280		1,850,092
Other Liabilities Notional [Member] | Interest Rate Contract [Member]
Derivatives designated as hedging instruments:
Interest rate contracts (2)		[2]		[2]
Other Liabilities Notional [Member] | Foreign Exchange Contract [Member]
Derivatives designated as hedging instruments:
Foreign exchange contracts	688,629		244,731
Interest Rate Contract [Member]
Derivatives designated as hedging instruments:
Interest rate contracts (2)	84,498	[1],[2]	74,368	[1],[2]
Interest rate contracts (2)		[1],[2]		[1],[2]
Foreign Exchange Contract [Member]
Derivatives designated as hedging instruments:
Foreign exchange contracts	19,079	[1]	43,226	[1]
Foreign exchange contracts	$ (27,259)	[1]	$ (12,161)	[1]

[1] Derivative instruments in an asset or liability position are included within Other Assets or Other Liabilities, respectively, in the consolidated balance sheet.

[2] At June 30, 2011 and December 31, 2010, the Company held net cash collateral related to these derivative positions of $32.9 million and $23.0 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 positions within the balance sheet as appropriate under the netting agreement.

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