Employee Share Plans - Stock Award Activity (Detail) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Compensation And Retirement Disclosure [Abstract]
Outstanding Beginning balance, Number of Options | shares	4,885
Granted, Number of Options | shares	654
Exercised, Number of Options | shares	(1,127)
Expired or canceled, Number of Options | shares	(36)
Outstanding Ending balance, Number of Options | shares	4,376
Vested and exercisable Ending balance, Number of Options | shares	2,215
Outstanding Beginning balance, Weighted Average Exercise Price Per Share | $ / shares	$ 7.50
Granted, Weighted Average Exercise Price Per Share | $ / shares	10.35
Exercised, Weighted Average Exercise Price Per Share | $ / shares	7.16
Expired or canceled, Weighted Average Exercise Price Per Share | $ / shares	7.56
Outstanding Ending balance, Weighted Average Exercise Price Per Share | $ / shares	8.02
Vested and exercisable Ending balance, Weighted Average Exercise Price | $ / shares	$ 7.08
Weighted Average Remaining Contractual Term, Outstanding	3 years 2 months 1 day
Weighted Average Remaining Contractual Term, Vested and exercisable at December 31, 2015	2 years 3 months
Aggregate Intrinsic Value, Outstanding Ending Balance | $	$ 24.9
Aggregate Intrinsic Value, Vested and exercisable at December 31, 2015 | $	$ 14.7