Changes In Fair Value of Level 3 Financial Assets (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of the period	$ 73,896	$ 99,154	$ 74,596	$ 146,044
Calls at par value		(13,100)	(225)	(64,600)
Other than Temporary Impairment Losses, Investments	0	0	(1,969)	0
(Increase) decrease in previously recognized unrealized losses included in other comprehensive income	950	(4,963)	2,444	(353)
Balance, end of the period	$ 74,846	$ 81,091	$ 74,846	$ 81,091