CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 5,901	$ 2,312
Long-term debt, debt discount and issuance costs	$ 5,352	$ 5,795
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	400,000,000	400,000,000
Common stock, issued	268,790,705	267,315,526
Common stock, outstanding	202,401,130	213,614,430
Treasury stock, shares	66,389,575	53,701,096