Contingencies - Narrative (Details) - USD ($)						9 Months Ended
	Jan. 27, 2017	Oct. 19, 2015	Feb. 17, 2015	Feb. 09, 2015	Jan. 27, 2015	Sep. 30, 2015	Sep. 30, 2014
Loss Contingencies [Line Items]
Minimum estimated range of aggregate loss for legal proceedings						$ 0
Maximum estimated range of aggregate loss for legal proceedings						50,000,000
Auction rate securities related to settlements with regulators, outstanding						75,000
Auction rate securities, firm purchased and hold						101,900,000
Amount of ARS committed to purchase from clients						9,500,000
Eligible investor subject to future buyback potential additional losses related to valuation adjustments						78,500,000
Eligible Investor Subject To Future Buyback Potential Additional Losses Related To Valuation Adjustments						$ 0
Period of auction rates security to be purchased from rendering of the award						30 days
Litigation settlement, expense							$ 20,000,000
Subsequent Event [Member]
Loss Contingencies [Line Items]
Litigation settlement, amount		$ 215,000
SEC [Member]
Loss Contingencies [Line Items]
Litigation settlement, amount					$ 10,000,000
Payments for legal settlements			$ 5,000,000
SEC [Member] | Disgorgement [Member]
Loss Contingencies [Line Items]
Litigation settlement, amount					4,200,000
SEC [Member] | Prejudgment Interest [Member]
Loss Contingencies [Line Items]
Litigation settlement, amount					753,500
SEC [Member] | Civil Penalties [Member]
Loss Contingencies [Line Items]
Litigation settlement, amount					5,100,000
United States Department of the Treasury [Member]
Loss Contingencies [Line Items]
Litigation settlement, amount					$ 10,000,000
Payments for legal settlements				$ 5,000,000
Forecast [Member] | SEC [Member]
Loss Contingencies [Line Items]
Payments for legal settlements	$ 5,000,000