Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Statement Of Financial Position [Abstract]
Property and equipment, accumulated depreciation (in dollars)	$ 680,238	$ 659,285
Intangible assets, excluding goodwill, accumulated amortization (in dollars)	$ 59,495	$ 64,615
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	112,848,000	116,986,000
Common stock, shares outstanding	112,264,000	116,725,000
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