STATUTORY FINANCIAL DATA (Detail) - Statutory capital and surplus for the principal operating subsidiaries of the Company (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Bermuda [Member]
Required statutory capital and surplus	$ 4,923,801	[1]	$ 4,687,988	[1]
Actual statutory capital and surplus (3)	9,140,393	[1],[2]	9,159,021	[1],[2]
U.S [Member]
Required statutory capital and surplus	637,799	[3]	640,834	[3]
Actual statutory capital and surplus (3)	2,093,694	[2],[3]	2,273,711	[2],[3]
U.K., Europe and Other [Member]
Required statutory capital and surplus	1,132,821		1,141,884
Actual statutory capital and surplus (3)	$ 3,197,220	[2]	$ 3,211,204	[2]

[1] Required statutory capital and surplus represents 100% BSCR level for principal Bermuda operating subsidiaries.

[2] Statutory assets in Bermuda include investments in other U.S. and international subsidiaries reported separately herein.

[3] Required statutory capital and surplus represents 100% RBC level for principal U.S. operating subsidiaries.