Investments - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2014 Securities	Dec. 31, 2013
Schedule of Investments [Line Items]
Non-credit OTTI on fixed maturities in an unrealized gain position	$ 700,000	$ 500,000
Number of securities transferred from Level 3 to Level 2	1
Equity Securities | Maximum
Schedule of Investments [Line Items]
Percentage of fair value under carrying value	80.00%
Mortgage-backed and asset-backed securities
Schedule of Investments [Line Items]
Securities, effective maturities	4 years 6 months
Non-government-backed securities
Schedule of Investments [Line Items]
Gross Unrealized Loss	$ 600,000	$ 1,100,000
Non-government-backed securities | Maximum
Schedule of Investments [Line Items]
Percentage of investment	5.00%	5.00%