Summary of Treasury Stock Activity (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) shares
Schedule of Treasury Stock [Line Items]
Beginning Balance, Shares | shares	4,057,135
Restricted stock withholdings | shares	108,472	[1]
Restricted stock forfeitures | shares	14,158
Ending Balance, Shares | shares	4,179,765
Beginning Balance, Cost	$ 61,807
Restricted stock withholdings	4,770	[1]
Restricted stock forfeitures	0
Ending Balance, Cost	$ 66,577

[1] The Company withheld restricted shares as a result of the election by certain employees to satisfy their tax liabilities upon vesting in restricted stock and restricted stock units. The Company determined the number of shares to be withheld based upon market values ranging from $35.44 to $44.67 per share.