Activity with Respect to Options Granted (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Shares
Beginning balance, shares	6,578,522
Granted, shares	459,375
Forfeited, shares	(60,498)
Exercised, shares	(33,468)
Expired, shares	(28,066)
Ending balance, shares	6,915,865	6,578,522
Nonvested, shares	3,136,492	3,106,083
Exercisable, shares	3,779,373
Weighted Average Exercise Price
Beginning Balance, Weighted Average Exercise Price	$ 87.52
Granted, Weighted Average Exercise Price	36.46
Forfeited, Weighted Average Exercise Price	66.73
Exercised, Weighted Average Exercise Price	21.44
Expired, Weighted Average Exercise Price	125.43
Ending Balance, Weighted Average Exercise Price	84.47	$ 87.52
Nonvested, Weighted Average Exercise Price	69.39
Exercisable, Weighted Average Exercise Price	$ 97.16
Weighted Average Remaining Contractual Term (years)
Weighted Average Remaining Contractual Term (years)	7 years 10 months 24 days	8 years
Nonvested, Weighted Average Remaining Contractual Term (years)	9 years 1 month 6 days
Exercisable, Weighted Average Remaining Contractual Term (years)	6 years 10 months 24 days
Aggregate Intrinsic Value
Beginning balance, Aggregate Intrinsic Value	$ 18,442
Exercised, Aggregate Intrinsic Value	481
Ending balance, Aggregate Intrinsic Value	26,584	$ 18,442
Nonvested, Aggregate Intrinsic Value	2,329
Exercisable, Aggregate Intrinsic Value	$ 24,255