Stock-based Compensation - Summary of Stock Option Activity (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Beginning Balance	190,160
Number of Shares, Granted	0
Number of Shares, Exercised	(14,270)
Number of Shares, Forfeited	0
Number of Shares, Ending Balance	175,890
Weighted Average Exercise Price, Beginning Balance	$ 20.11
Weighted Average Exercise Price, Granted	$ 0
Weighted Average Exercise Price, Exercised	$ 28.33
Weighted Average Exercise Price, Forfeited	$ 0
Weighted Average Exercise Price, Ending Balance	$ 19.44