Financial Data Pertaining to the Different Trusts (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Debt Disclosure [Line Items]
Junior subordinated debentures, redemption price percentage	100.00%
Junior subordinates debentures, discount	$ 478,995
Fixed Rate 5.00 Percent Until December 2013 And 9.00 Percent Thereafter Junior Subordinated Deferrable Interest Debentures with no Stated Maturity
Debt Disclosure [Line Items]
Junior subordinated debentures, description of redemption price	the junior subordinated debentures at a redemption price equal to 100% of the principal amount, plus accrued and unpaid interest to the date of redemption.
Junior subordinates debentures, carrying value	457,005	444,981	433,887
Junior subordinates debentures, aggregate liquidation amount	936,000	936,000	936,000
Junior subordinates debentures, discount	$ 478,995	$ 491,000	$ 502,113