Investments - Progression of Credit-Related Portion of OTTI on Investments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Investments Debt And Equity Securities [Abstract]
Beginning balance	$ (2,632)	$ (2,599)	$ (2,632)	$ (2,666)
Additional credit impairments on:
Previously impaired securities		(33)		(61)
Securities without previous impairments	0	0	0	0
Total additional credit impairments securities		(33)		(61)
Reductions for securities sold (realized)				95
Ending balance	$ (2,632)	$ (2,632)	$ (2,632)	$ (2,632)