Stock Options (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Shares
Beginning balance, shares	3,106,083
Granted, shares	459,375
Vested/Issued, shares	(368,468)
Forfeited, shares	(60,498)
Ending balance, shares	3,136,492
Weighted Average Grant-Date Fair Value
Beginning balance, Weighted Average Grant-Date Fair Value	$ 47.78
Granted, Weighted Average Grant-Date Fair Value	22.86	$ 36.28
Vested/Issued, Weighted Average Grant-Date Fair Value	72.27
Forfeited, Weighted Average Grant-Date Fair Value	39.80
Ending balance, Weighted Average Grant-Date Fair Value	$ 41.50