Accrued Bonus Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Compensation Related Costs [Abstract]
Accrued employee's bonus compensation	$ 14.1	$ 7.7
Percentage of earnings	8.50%	8.50%
Accrued employee's bonus compensation paid in cash	$ 12.1
Awarded its directors, executive officers and select employees' bonus compensation, total		$ 7.2	$ 11.5
Awarded its directors, executive officers and select employees' bonus compensation, cash			6.4
Awarded its directors, executive officers and select employees' bonus compensation, ownership equity			$ 5.1
Awarded its directors, executive officers and select employees' bonus compensation, ownership equity, shares			389
Awarded its directors, executive officers and select employees' bonus compensation, ownership equity, share price			$ 13,125