Commitments and Contingencies - Additional Information (Detail) - American Interstate Insurance Company [Member] - Iowa [Member] - USD ($) $ in Millions	1 Months Ended
	Feb. 28, 2015	Sep. 30, 2015
Loss Contingencies [Line Items]
Appeal bond		$ 27.8
2009 Workers' Compensation Claim [Member]
Loss Contingencies [Line Items]
Workers compensation claim, damages awarded	$ 25.3
Workers compensation claims contingency reserves		$ 2.6
Plaintiff Seeking Actual Damages [Member]
Loss Contingencies [Line Items]
Amount of damages	0.3
Plaintiff Seeking Punitive Damages [Member]
Loss Contingencies [Line Items]
Amount of damages	$ 25.0