Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Statement Of Financial Position [Abstract]
Property and equipment, accumulated depreciation (in dollars)	$ 636,099	$ 611,021
Intangible assets, excluding goodwill, accumulated amortization (in dollars)	$ 137,767	$ 132,724
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, Authorized shares	500,000,000	500,000,000
Common stock, shares issued	120,566,000	120,145,000
Common stock, shares outstanding	120,107,000	119,926,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, Authorized shares	50,000,000	50,000,000
Preferred stock, shares issued	0	0