Investments - Credit Quality Indicators (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Financing Receivable, Recorded Investment [Line Items]
Total asset-based loans	$ 565.6	$ 181.5
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total asset-based loans	306.9	91.6
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total asset-based loans	36.7	89.9
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total asset-based loans	222.0
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total asset-based loans