Summary of Activity Related to Other-Than-Temporary Impairment Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended						12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013 Investment	Dec. 31, 2012 Investment	Dec. 31, 2011 Investment
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Number of Securities							4	4	22
Total other-than-temporary impairment losses	$ 530	$ 1,821	$ 42	$ 208	$ 496	$ 198	$ 2,393	$ 902	$ 3,617
Portion of loss recognized in other comprehensive income						44		44	1,632
Net other-than-temporary impairment losses recognized in earnings	530	1,821	42	208	496	154	2,393	858	1,985
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							1,822		109
Net other-than-temporary impairment losses recognized in earnings							1,822		109
Residential Mortgage Backed Securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Number of Securities								1	19
Total other-than-temporary impairment losses								55	2,616
Portion of loss recognized in other comprehensive income								44	1,632
Net other-than-temporary impairment losses recognized in earnings								11	984
Equity Securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Number of Securities							3	3	2
Total other-than-temporary impairment losses							571	847	892
Net other-than-temporary impairment losses recognized in earnings							$ 571	$ 847	$ 892