Employee Benefit Plans - Time-Based Restricted Stock Unit Equity Awards (Details) - Restricted Stock Units (RSUs) [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2016 USD ($) grant_recipient $ / shares shares	Sep. 30, 2015 USD ($) grant_recipient $ / shares shares
Number of Restricted Stock Units
Outstanding at beginning of year, shares | shares	1,978,262	26,668
Granted, shares | shares	2,117,330	2,036,900
Vested, shares | shares	(423,427)	(12,221)
Cancelled, shares | shares	(193,932)	(73,085)
Outstanding at end of year, shares | shares	3,478,233	1,978,262
Weighted Average Grant Date Fair Value
Outstanding at beginning of year, weighted average grant date fair value, per share | $ / shares	$ 25.60	$ 21.49
Granted, weighted average grant date fair value, per share | $ / shares	23.14	26.02
Vested, weighted average grant date fair value, per share | $ / shares	25.57	21.48
Cancelled, weighted average grant date fair value, per share | $ / shares	25.05	26.06
Outstanding at end of year, weighted average grant date fair value, per share | $ / shares	$ 24.12	$ 25.60
Additional information - restricted stock units
Share-based compensation expense | $	$ 18.7	$ 9.4
Unrecognized compensation expense | $	$ 56.0
Weighted average period over which unrecognized compensation cost is expected to be recognized	3 years 9 months
Minimum [Member]
Additional information - restricted stock units
Vesting period	1 year
Fiscal 2016 Grant [Member]
Additional information - restricted stock units
RSU grant recipients | grant_recipient	570
Fiscal 2015 Grant [Member]
Additional information - restricted stock units
RSU grant recipients | grant_recipient		580
Fiscal 2015 Grant [Member] | Minimum [Member]
Additional information - restricted stock units
Vesting period		3 years
Fiscal 2015 Grant [Member] | Maximum [Member]
Additional information - restricted stock units
Vesting period		5 years