Stock Compensation - Summary of Stock Option Activity (Detail) $ / shares in Units, shares in Thousands, $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($) $ / shares shares
Stock Options
Outstanding at beginning of period (in shares) | shares	1,758
Granted (in shares) | shares	0
Exercised (in shares) | shares	(1)
Forfeited and expired (in shares) | shares	(597)
Outstanding at end of period (in shares) | shares	1,160
Expected to vest at end of period (in shares) | shares	6
Exercisable at end of period (in shares) | shares	1,154
Weighted- Average Exercise Price
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 26.35
Granted (in dollars per share) | $ / shares	0.00
Exercised (in dollars per share) | $ / shares	15.66
Forfeited and expired (in dollars per share) | $ / shares	23.72
Outstanding at end of period (in dollars per share) | $ / shares	27.72
Expected to vest at end of period (in dollars per share) | $ / shares	11.99
Exercisable at end of period (in dollars per share) | $ / shares	$ 27.81
Weighted- Average Remaining Contractual Term (years)
Outstanding at end of period	1 year 5 months 1 day
Expected to vest at end of period	4 years 2 months 12 days
Exercisable at end of period	1 year 4 months 28 days
Aggregate Intrinsic Value
Outstanding at end of period | $	$ 0.2
Expected to vest at end of period | $	0.1
Exercisable at end of period | $	$ 0.2