Employee Benefit Plans (Details) (USD $)	12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011 Employee Completing One Year of Service [Member]	Sep. 30, 2012 Employee Completing One Year of Service [Member]	Sep. 30, 2010 Employee Completing One Year of Service [Member]	Sep. 30, 2012 Union Sponsored Defined Benefit Plan [Member]	Sep. 30, 2011 Union Sponsored Defined Benefit Plan [Member]	Sep. 30, 2010 Union Sponsored Defined Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, percentage of contribution from salary	75.00%
Defined Benefit Plan, Employee Contributions, Statutory Maximum Per Employee	$ 17,000
Minimum Service Period Required To Match Contributions For Employees	1 year
Minimum number of working hours required within one year of service	1000 hours
Contributions by Inergy for employees		$ 200,000	$ 200,000	$ 200,000	$ 100,000	$ 100,000	$ 100,000