Credit Losses Recognized in Earnings for Debt Securities Where Portion of OTTI Recognized in OCI (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013	Dec. 31, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Beginning balance	$ 7,798	[1]	$ 7,478	$ 7,478	[1]
Additions for credit losses on securities previously recognized	232
Ending balance	$ 8,030		$ 7,478	$ 7,478	[1]

[1] The beginning balance includes credit related losses included in OTTI charges recognized on debt securities in prior periods.