Share-Based Compensation - Summary of Stock Option Activity (Details) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares
Shares
Outstanding, September 30, 2016 (in shares) | shares		0
Converted on October 1, 2016 (in shares) | shares		500,000
Granted (in shares) | shares	0	0
Exercised (in shares) | shares		0
Forfeited (in shares) | shares		0
Outstanding at March 31, 2017 (in shares) | shares	500,000	500,000
Weighted Average Exercise Price
Outstanding, September 30, 2016 (in dollars per share) | $ / shares		$ 0.00
Converted on October 1, 2016 (in dollars per share) | $ / shares		18.37
Granted (in dollars per share) | $ / shares		0.00
Exercised (in dollars per share) | $ / shares		0.00
Forfeited (in dollars per share) | $ / shares		0.00
Outstanding at March 31, 2017 (in dollars per share) | $ / shares	$ 18.36	$ 18.36
Weighted average remaining contractual terms, options outstanding		5 years 8 months 12 days
Aggregate intrinsic value, options outstanding | $	$ 7.2	$ 7.2
Weighted average remaining contractual terms, options exercisable		5 years 7 months 6 days
Aggregate intrinsic value, options exercisable | $	$ 7.0	$ 7.0