Net Income Per Share - Calculations of Basic and Diluted Net Income per Share and Basic and Dilutive Weighted Average Shares Outstanding (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Net income	$ 38,275	$ 46,284	$ 59,217	$ 38,066	$ 84,559	$ 97,282
Weighted average shares outstanding (in shares)	68,114		70,428		68,277	70,708
Dilutive impact from:
Share-based payment awards (in shares)	730		720		813	892
Dilutive weighted average shares outstanding (in shares)	68,844		71,148		69,090	71,600
Income per share
Basic (in dollars per share)	$ 0.56		$ 0.84		$ 1.24	$ 1.38
Dilutive (in dollars per share)	$ 0.56		$ 0.83		$ 1.22	$ 1.36