Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011	Jul. 31, 2012 Swiss Re Financial Products Corporation	Sep. 30, 2013 Swiss Re Financial Products Corporation	Sep. 30, 2013 Maximum	Sep. 30, 2013 Noncompete Agreements	Sep. 30, 2013 Customer Lists Minimum	Sep. 30, 2013 Customer Lists Maximum	Sep. 30, 2013 Trade Names Minimum	Sep. 30, 2013 Trade Names Maximum
Schedule Of Significant Accounting Policies [Line Items]
Finance charge income	$ 5,521,000	$ 4,393,000	$ 4,814,000
Cash equivalents, highly liquid investments maturity						3 months
Intangible assets, amortization period							5 years	7 years	10 years	7 years	20 years
Advertising and direct mail expenses	10,500,000	9,600,000	9,500,000
weather hedge contract, payment entitled to be received per heating degree-day shortfall				35,000
Percentage in heating degree days less than ten year average that is covered				92.50%
Derivative maximum payout					$ 12,500,000