Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Sep. 30, 2017
Statement Of Financial Position [Abstract]
Property and equipment, accumulated depreciation (in dollars)	$ 593,545	$ 546,061
Intangible assets, excluding goodwill, accumulated amortization (in dollars)	$ 130,057	$ 121,550
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	120,226,000	129,710,000
Common stock, shares outstanding	119,882,000	129,585,000
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