Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 10,243	$ 10,462
Accumulated depreciation and amortization of property and equipment	255,916	331,700
Accumulated amortization of intangible assets	$ 65,922	$ 52,942
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	3,000,000	3,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	35,251,000	35,482,000
Common stock, shares outstanding	35,251,000	35,482,000