Commitments and Contingencies - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013 Policies	Apr. 30, 2013 Ambac [Member]	Apr. 30, 2013 Segregated Account [Member]
Contingencies And Commitments [Line Items]
Minimum percentage of payments on permitted policy claims	25.00%
Number of policies considered for Supplemental Payments	14
Payment to settle the IRS dispute and related proceedings		$ 1,900	$ 100,000