INVESTMENTS (Detail) - Contractual maturities of available for sale securities and held to maturity income securities (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Fixed maturities - AFS
Due less than one year	$ 2,025,446	[1]	$ 1,583,265	[1]
Due less than one year	2,041,814	[1]	1,570,909	[1]
Due after 1 through 5 years	7,874,145	[1]	9,021,926	[1]
Due after 1 through 5 years	8,049,150	[1]	9,118,229	[1]
Due after 5 through 10 years	3,788,673	[1]	4,137,260	[1]
Due after 5 through 10 years	3,953,496	[1]	4,198,362	[1]
Due after 10 years	3,275,281	[1]	3,228,553	[1]
Due after 10 years	3,504,551	[1]	3,161,894	[1]
	16,963,545	[1]	17,971,004	[1]
	17,549,011	[1]	18,049,394	[1]
Available for sale fixed income securities, Amortized Cost	25,771,715	[1]	27,322,842	[1]
Available for sale fixed income securities, Fair Value	26,190,025	[1]	27,142,105	[1]
Fixed maturities - HTM
Due less than one year	11,796	[1]	0	[1]
Due less than one year	11,768	[1]	0	[1]
Due after 1 through 5 years	122,091	[1]	125,449	[1]
Due after 1 through 5 years	123,871	[1]	125,416	[1]
Due after 5 through 10 years	393,865	[1]	348,797	[1]
Due after 5 through 10 years	402,424	[1]	346,494	[1]
Due after 10 years	1,779,587	[1]	1,884,217	[1]
Due after 10 years	1,968,629	[1]	1,901,032	[1]
	2,307,339	[1]	2,358,463	[1]
	2,506,692	[1]	2,372,942	[1]
Held to maturity income securities, Amortized Cost	2,668,978	[1]	2,728,335	[1]
Held to maturity income securities, Fair Value	2,895,688	[1]	2,742,626	[1]
Residential Mortgage Backed Securities [Member] | Agency Securities [Member]
Fixed maturities - AFS
Available for sale fixed income securities, Amortized Cost	5,189,473	[1]	5,059,249	[1]
Available for sale fixed income securities, Fair Value	5,379,406	[1]	5,203,711	[1]
Residential Mortgage Backed Securities [Member] | Non-Agency [Member]
Fixed maturities - AFS
Available for sale fixed income securities, Amortized Cost	851,557	[1]	1,257,474	[1]
Available for sale fixed income securities, Fair Value	641,815	[1]	1,021,823	[1]
Fixed maturities - HTM
Held to maturity income securities, Amortized Cost	80,955	[1]	82,763	[1]
Held to maturity income securities, Fair Value	87,443	[1]	82,851	[1]
Commercial Mortgage Backed Securities [Member]
Fixed maturities - AFS
Available for sale fixed income securities, Amortized Cost	927,684	[1]	1,135,075	[1]
Available for sale fixed income securities, Fair Value	974,835	[1]	1,172,507	[1]
Collateralized Debt Obligations [Member]
Fixed maturities - AFS
Available for sale fixed income securities, Amortized Cost	843,553	[1]	920,501	[1]
Available for sale fixed income securities, Fair Value	658,602	[1]	734,138	[1]
Other Asset Backed Securities [Member]
Fixed maturities - AFS
Available for sale fixed income securities, Amortized Cost	995,903	[1]	979,539	[1]
Available for sale fixed income securities, Fair Value	986,356	[1]	960,532	[1]
Fixed maturities - HTM
Held to maturity income securities, Amortized Cost	280,684	[1]	287,109	[1]
Held to maturity income securities, Fair Value	301,553	[1]	286,833	[1]
Mortgage and Asset Backed Securities [Member]
Fixed maturities - AFS
Available for sale fixed income securities, Amortized Cost	8,808,170	[1]	9,351,838	[1]
Available for sale fixed income securities, Fair Value	8,641,014	[1]	9,092,711	[1]
Fixed maturities - HTM
Held to maturity income securities, Amortized Cost	361,639	[1]	369,872	[1]
Held to maturity income securities, Fair Value	$ 388,996	[1]	$ 369,684	[1]

[1] Included in the table above are Tier One and Upper Tier Two securities, representing committed term debt and hybrid instruments, which are senior to the common and preferred equities of the financial institutions, at their fair value of $386.1 million and $757.8 million at December 31, 2011 and 2010, respectively. These securities are reflected in the table based on their call date and have net unrealized losses of $108.8 million and $143.7 million at December 31, 2011 and 2010, respectively.