Stockholders Equity - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2014	Dec. 31, 2015	Dec. 31, 2014
Stockholders Equity [Line Items]
Common stock, authorized shares		50,000,000	50,000,000
Common stock, par value		$ 0.10	$ 0.10
Preferred stock, authorized shares		1,000,000	1,000,000
Preferred stock, par value		$ 0.10	$ 0.10
Undistributed Profit	$ 156,700,000
Dividend Capacity		$ 1,100,000
Navigators Insurance Company
Stockholders Equity [Line Items]
Maximum amount available for payment of dividends without prior regulatory approval		94,900,000
Payment of dividends		$ 0	$ 0