Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		0 Months Ended			0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Dec. 12, 2013 Revolving Credit Facility	Mar. 31, 2014 Revolving Credit Facility	Sep. 30, 2013 Revolving Credit Facility	Dec. 12, 2013 Revolving Credit Facility Minimum	Dec. 12, 2013 Revolving Credit Facility Maximum	Mar. 31, 2014 Letters of credit	Dec. 12, 2013 Letters of credit Maximum
Long-Term Debt
Amount available for borrowing					$ 15.0						$ 3.0
Period by which maturity date is extended					3 years
Additional maximum borrowing capacity									10.0
Unused commitment fee before amendment (as a percent)					0.20%
Unused commitment fee (as a percent)								0.15%	0.35%
Amount outstanding						0	0
Amount of letter of credit undrawn, issued and outstanding										0.7
Available balance under credit facility						14.3	15.0
Gross interest expense	$ 0.7	$ 0.4	$ 1.4	$ 0.7