Employee Benefit Plans - Stock Options (Details) - Employee Stock Option [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2014 USD ($) grant_recipient $ / shares shares
Stock Options
Outstanding at beginning of year, shares | shares	15,337,656	19,478,811	18,962,536
Granted, shares | shares	0	0	3,856,166
Exercised, shares | shares	(3,504,989)	(3,636,655)	(2,687,724)
Canceled or expired, shares | shares	(436,750)	(504,500)	(652,167)
Outstanding at end of year, shares | shares	11,395,917	15,337,656	19,478,811
Exercisable at end of year, shares | shares	6,645,967	6,859,889	7,207,978
Weighted Average Exercise Price
Outstanding at beginning of year, weighted average exercise price, per share	$ 17.50	$ 17.37	$ 15.91
Granted, weighted average exercise price, per share	0.00	0.00	23.85
Exercised, weighted average exercise price, per share	31.21	28.75	16.30
Canceled or expired, weighted average exercise price, per share	18.45	19.89	17.68
Outstanding at end of year, weighted average exercise price, per share	16.69	17.50	17.37
Exercisable at end of year, weighted average exercise price, per share	$ 14.99	$ 16.51	$ 16.27
Assumptions used in Black-Scholes option valuation model
Risk free interest rate			2.01%
Expected life (in years)			6 years 5 months 24 days
Expected volatility			48.80%
Expected dividend yield			0.63%
Additional information - stock options
Expiration period	10 years		10 years
Total intrinsic value of options exercised | $	$ 39.2	$ 44.6	$ 18.0
Aggregate intrinsic value of options outstanding | $	154.0
Aggregate intrinsic value of options exercisable | $	$ 101.1
Lower range of options outstanding exercise price	$ 9.03
Upper range of options outstanding exercise price	$ 23.86
Weighted average remaining contractual term of options outstanding	4 years 9 months
Weighted average remaining contractual term of options exercisable	4 years 7 months
Stock Option Grant Recipients | grant_recipient			520
Weighted average fair value per share of options granted			$ 11.21
Stock based compensation expense | $	$ 20.5	$ 28.9	$ 25.5
Unrecognized compensation expense related to options | $	$ 23.8
Weighted average period over which unrecognized compensation cost is expected to be recognized	2 years 1 month
Minimum [Member]
Additional information - stock options
Vesting period	2 years		3 years
Maximum [Member]
Additional information - stock options
Vesting period	9 years 9 months		5 years