Stock Option Activity (Detail)	3 Months Ended
	Mar. 31, 2016 $ / shares shares
Underlying Shares
Outstanding at beginning of period | shares	6,307,250
Granted | shares	50,000
Expired | shares	(30,000)
Outstanding at end of period | shares	6,327,250
Exercisable at end of year | shares	5,332,768
Weighted Average Exercise Price
Outstanding at beginning of period | $ / shares	$ 21.68
Granted | $ / shares	15.08
Expired | $ / shares	34.24
Outstanding at end of period | $ / shares	21.56
Exercisable at end of year | $ / shares	$ 21.46