Long-term Debt (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended			12 Months Ended			1 Months Ended	12 Months Ended
	Sep. 30, 2014 Senior Secured Notes 7.625 Percent Due April 2019	Sep. 30, 2011 Senior Secured Notes 7.625 Percent Due April 2019	Sep. 30, 2013 Senior Secured Notes 7.625 Percent Due April 2019	Sep. 30, 2014 Senior Secured Notes 7.625 Percent Due April 2019 Debt Instrument, Redemption Period Commencing after March 31, 2015 Maximum	Sep. 30, 2014 Senior Secured Notes 7.625 Percent Due April 2019 Debt Instrument, Redemption Period Commencing after March 31, 2015 Minimum	Sep. 30, 2014 Senior Secured Notes 7.625 Percent Due April 2019 Debt Instrument, Redemption Period on or Prior to March 31, 2015	Dec. 31, 2013 Senior Notes 7.25 Percent Due January 2019	Sep. 30, 2014 Senior Notes 7.25 Percent Due January 2019	Sep. 30, 2014 Senior Notes 7.25 Percent Due January 2019 Debt Instrument Redemption Period Commencing after January 15, 2016 Maximum	Sep. 30, 2014 Senior Notes 7.25 Percent Due January 2019 Debt Instrument Redemption Period Commencing after January 15, 2016 Minimum	Sep. 30, 2014 Senior Notes 7.25 Percent Due January 2019 Debt Instrument Redemption Period on or Prior to January 15, 2016	Sep. 30, 2014 Senior Notes 7.25 Percent Due January 2019 Debt Instrument Redemption Period on or Prior to January 15, 2016 Maximum
Long-term debt
Additional borrowings		$ 400.0					$ 150.0
Net proceeds from senior secured notes		$ 392.8					$ 146.7
Interest rate on secured notes (as a percent)	7.625%	7.625%	7.625%				7.25%	7.25%
Debt instrument redemption price (as a percent)				103.80%	100.00%				103.625%	100.00%
Percentage of the principal amount of the debt instrument which the entity may redeem with proceeds from qualified equity offerings												35.00%
Redemption price of debt instrument if redeemed with proceeds from qualified equity offerings (as a percent)											107.25%
Debt instrument redemption price in addition to a make-whole premium (as a percent)						100.00%					100.00%
Purchase price of debt instrument, if there is a change in control (as a percent)	101.00%							101.00%