Contingencies - Narrative (Details) - USD ($)					3 Months Ended
	Jan. 27, 2017	Feb. 17, 2015	Feb. 09, 2015	Jan. 27, 2015	Mar. 31, 2016
Loss Contingencies [Line Items]
Minimum estimated range of aggregate loss for legal proceedings					$ 0
Maximum estimated range of aggregate loss for legal proceedings					49,000,000
Auction rate securities, firm purchased and hold					87,100,000
Amount of ARS committed to purchase from clients					32,500,000
Eligible investor subject to future buyback potential additional losses related to valuation adjustments					37,300,000
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
Forecast [Member] | SEC [Member]
Loss Contingencies [Line Items]
Payments for legal settlements	$ 5,000,000