Share Based Compensation - Stock Option Activity under Stock Option Plans (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2011
Number of Shares
Beginning balance (in shares)	906,636
Granted (in shares)	184,269
Exercised (in shares)	(13,750)
Cancelled (in shares)	(118,369)
Ending balance (in shares)	958,786
Vested and Expected to Vest (in shares)	958,786
Exercisable (in shares)	907,986
Weighted-Average Exercise Price
Beginning balance (usd per share)	$ 21.58	$ 22.57
Granted (usd per share)	$ 16.50
Exercised (usd per share)	$ 7.77
Cancelled (usd per share)	$ 23.42
Ending balance (usd per share)	$ 21.32	$ 22.57
Vested and Expected to Vest (usd per share)	$ 21.32
Exercisable (usd per share)	$ 21.74
Weighted Average Remaining Contractual Term
Outstanding (in years)	3 years 3 months 12 days
Vested and Expected to Vest (in years)	3 years 3 months 12 days
Exercisable (in years)	2 years 11 months 24 days
Aggregate Intrinsic Value
Outstanding	$ 3,064,900
Vested and Expected to Vest	3,064,900
Exercisable	$ 2,603,971