NOTES PAYABLE AND DEBT AND FINANCING ARRANGEMENTS (Detail) - Schedule of Letter of Credit Facilities (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Collateralized by certain of the Company’s investment portfolio	93.80%	[1]	21.10%	[2]
Revolving Credit Facilities [Member]
Letter of credit facilities	1,000,000	[1],[3]	1,000,000	[2],[3]
Letter of Credit [Member]
Letter of credit facilities	4,000,000	[1],[4]	5,000,114	[2],[4]
Available letter of credit facilities – in use	1,871,192	[1]	2,395,242	[2]

[1] At December 31, 2011 there were five available letter of credit facilities.

[2] At December 31, 2010 there were five available letter of credit facilities.

[3] At December 31, 2011 and 2010 the revolving credit facilities were unutilized

[4] The Company has the option to increase the size of the March 2011 Credit Agreement by an additional $500 million and the size of the facilities under the December 2011 Credit Agreements by an additional $500 million across both such facilities.