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Equity and Stock-based Compensation - Summary of RSU Activity (Detail) - $ / shares
shares in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Unvested, Shares, Beginning Balance 1,211    
Unvested, Shares, Ending Balance 1,562 1,211  
Granted, Fair value at Grant $ 26.59 $ 19.37 $ 29.66
Restricted Stock Unit [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Unvested, Shares, Beginning Balance 1,211    
Granted, Shares 978    
Vested, Shares (563)    
Forfeited, Shares (64)    
Unvested, Shares, Ending Balance 1,562 1,211  
Unvested, Fair value at Grant, Beginning Balance $ 21.60    
Granted, Fair value at Grant 26.59    
Vested, Fair value at Grant 21.34    
Forfeited, Fair value at Grant 23.34    
Unvested, Fair value at Grant, Ending Balance $ 24.75 $ 21.60