Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2019	Sep. 30, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, authorized	50,000,000	50,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	500,000,000	500,000,000
Common stock, issued	104,962,000	104,470,000
Common stock, outstanding	104,962,000	104,470,000