Description of Business and Summary of Significant Accounting Policies - Reconciliation of Basic to Diluted Shares Outstanding (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Shares used in net income per common share - basic	37,868	28,949	25,719
Dilutive effect of the equity premium on Convertible Notes at the average price of common stock			132
Incremental shares of unvested restricted common stock	512	115	21
Shares used in net income per common share - diluted	38,380	29,064	25,872