Statutory Financial Information - Additional Information (Detail) - Wright Flood - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Statutory Accounting Practices [Line Items]
Statutory capital and surplus required	$ 7,500,000
Statutory capital and surplus	23,500,000	$ 15,100,000
Statutory net Income	$ 8,200,000	$ 4,100,000