Summary of Activity under Stock-Based Compensation Plans (Detail)	6 Months Ended
	Jun. 30, 2015 USD ($) $ / shares shares
Stock Options Number Outstanding
Beginning Balance | shares	897,115
Cancelled or Expired | shares	(70,075)
Exercised | shares	(5,180)
Ending Balance | shares	821,860
Vested or expected to vest at June 30, 2015 | shares	763,031
Exercisable at June 30, 2015 | shares	402,168
Stock Options Average Exercise Price per share
Beginning Balance | $ / shares	$ 12.09
Cancelled or Expired | $ / shares	18.14
Exercised | $ / shares	8.01
Ending Balance | $ / shares	11.60
Vested or expected to vest at June 30, 2015 | $ / shares	11.80
Exercisable at June 30, 2015 | $ / shares	$ 14.04
Stock Options Remaining Contractual Life (in years)
Remaining Contractual Life	7 years 1 month 13 days
Vested or expected to vest at June 30, 2015	6 years 11 months 23 days
Exercisable at June 30, 2015	5 years 7 months 13 days
Stock Options Aggregate Intrinsic Value
Beginning Balance | $	$ 3,425,558
Ending Balance | $	59,279
Vested or expected to vest at June 30, 2015 | $	53,864
Exercisable at June 30, 2015 | $	$ 22,627