Summary of Activity Related to Other-Than-Temporary Impairment Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013 Investment	Sep. 30, 2013 Investment	Sep. 30, 2012 Investment
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Number of Securities	1	3	4
Total other-than-temporary impairment losses	$ 1,821	$ 1,863	$ 693
Portion of loss recognized in other comprehensive income			43
Net other-than-temporary impairment losses recognized in earnings	1,821	1,863	650
Corporate And Other Bonds
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Number of Securities	1	1
Total other-than-temporary impairment losses	1,821	1,821
Net other-than-temporary impairment losses recognized in earnings	1,821	1,821
Residential Mortgage Backed Securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Number of Securities			1
Total other-than-temporary impairment losses			54
Portion of loss recognized in other comprehensive income			43
Net other-than-temporary impairment losses recognized in earnings			11
Equity Securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Number of Securities		2	3
Total other-than-temporary impairment losses		42	639
Net other-than-temporary impairment losses recognized in earnings		$ 42	$ 639