Stock Option Activity (Detail)	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Number of Shares
Options outstanding, January 1, 2015 | shares	10,148,087
Granted | shares	1,095,500
Forfeited | shares	(541,138)
Exercised | shares	(638,743)
Options outstanding, September 30, 2015 | shares	10,063,706
Weighted Average Exercise Price Per Share
Options outstanding, January 1, 2015	$ 10.09
Granted	7.87
Forfeited	10.27
Exercised	5.84
Options outstanding, September 30, 2015	$ 10.11