Summary of Activity under Stock-Based Compensation Plans (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
Stock Options Number Outstanding
Beginning Balance | shares	832,941
Cancelled or Expired | shares	(52,004)
Ending Balance | shares	780,937
Vested or expected to vest at March 31, 2017 | shares	757,061
Exercisable at March 31, 2017 | shares	462,348
Stock Options Average Exercise Price per share
Beginning Balance | $ / shares	$ 7.11
Cancelled or Expired | $ / shares	13.61
Ending Balance | $ / shares	6.66
Vested or expected to vest at March 31, 2017 | $ / shares	6.72
Exercisable at March 31, 2017 | $ / shares	$ 7.82
Stock Options Remaining Contractual Life (in years)
Remaining Contractual Life	7 years 3 months 15 days
Vested or expected to vest at March 31, 2017	7 years 2 months 27 days
Exercisable at March 31, 2017	6 years 2 months 5 days
Stock Options Average Intrinsic Value
Average intrinsic value | $	$ 1,309,182
Vested or expected to vest at March 31, 2017 | $	1,248,383
Exercisable at March 31, 2017 | $	$ 552,005