Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 5,822	$ 4,720
Intangible assets, accumulated amortization	8,794	7,378
Property and equipment, accumulated depreciation and amortization	$ 93,159	$ 85,440
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	1,400,000,000	1,400,000,000
Common stock, shares issued (in shares)	119,933,386	119,771,702
Common stock, shares outstanding (in shares)	119,933,386	119,771,702
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000