Stock-Based Compensation Plans and Arrangements - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Options
Beginning balance (in shares)	7,595,059
Granted (in shares)	0
Exercised (in shares)	(2,693,347)
Canceled (in shares)	(440,719)
Ending balance (in shares)	4,460,993	7,595,059
Exercisable (in shares)	4,460,993
Weighted Average Exercise Price per Share
Beginning balance (in dollars per share)	$ 10.43
Granted (in dollars per share)	0.00
Exercised (in dollars per share)	5.80
Canceled (in dollars per share)	15.82
Ending balance (in dollars per share)	11.34	$ 10.43
Exercisable (in dollars per share)	$ 5.38
Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term, Outstanding, ending balance (in years)	1 year 1 month 25 days
Weighted Average Remaining Contractual Term, Exercisable, ending balance (in years)	1 year 1 month 25 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding, ending balance	$ 26,413
Aggregate Intrinsic Value, Exercisable, ending balance	26,413
Total intrinsic value of options exercised	16,500	$ 9,300	$ 13,700
Cash received from option exercises	100
Tax benefit from exercise of stock options	$ 2,700