Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 4,247	$ 4,880
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	64,802,000	64,495,000
Common stock, shares outstanding (in shares)	52,114,000	51,807,000
Treasury stock at cost (in shares)	12,688,000	12,688,000