Contingencies - Narrative (Details) - USD ($)						6 Months Ended
	Jan. 27, 2017	Jun. 07, 2016	Feb. 17, 2015	Feb. 09, 2015	Jan. 27, 2015	Jun. 30, 2016
Loss Contingencies [Line Items]
Minimum estimated range of aggregate loss for legal proceedings						$ 0
Maximum estimated range of aggregate loss for legal proceedings						54,000,000
Auction rate securities, firm purchased and hold						90,700,000
Amount of ARS committed to purchase from clients						26,900,000
Eligible investor subject to future buyback potential additional losses related to valuation adjustments						34,300,000
Eligible Investor Subject To Future Buyback Potential Additional Losses Related To Valuation Adjustments						0
Litigation settlement, expense						$ 10,000,000
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
FINRA Case [Member]
Loss Contingencies [Line Items]
Litigation settlement, amount		$ 2,300,000
FINRA Case [Member] | Eligible Clients
Loss Contingencies [Line Items]
Litigation settlement, amount		$ 717,000
Forecast [Member] | SEC [Member]
Loss Contingencies [Line Items]
Payments for legal settlements	$ 5,000,000