Stock-Based Compensation - Restricted Stock Plan Table (Details) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended	12 Months Ended
	Mar. 31, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	1,110,008	1,154,862
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	363,638
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Period Increase (Decrease)	(75,699)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	75,699
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	(134,646)
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	1,110,008	1,154,862
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	250,210	363,638
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures	30,845
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(54,481)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 20.20	$ 20.53
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 19.69
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$ 20.20
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 21.68
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms	2 years 1 month 10 days	1 year 8 months 27 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Intrinsic Value	$ 4,700,000	$ 7,400,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 3.8
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition - Restricted Stock	2 years 1 month 10 days