Commitments and Contingencies - Additional Information (Details) - USD ($)					12 Months Ended
	Jan. 27, 2017	Feb. 17, 2015	Feb. 09, 2015	Jan. 27, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Loss Contingencies [Line Items]
Operating leases expiring at various dates through					2028
Rent expense					$ 45,900,000	$ 45,600,000	$ 46,400,000
Capital commitments relating to investments					5,100,000
Minimum estimated range of aggregate loss for legal proceedings					0
Maximum estimated range of aggregate loss for legal proceedings					51,000,000.0
Auction rate securities related to settlements with regulators					5,000,000
Eligible investor subject to future buyback principal value					57,000,000
Eligible investor subject to future buyback potential additional losses related to valuation adjustments					0
Litigation settlement, expense					10,000,000
SEC
Loss Contingencies [Line Items]
Litigation settlement, amount				$ 10,000,000.0
Payments for legal settlements		$ 5,000,000
SEC | Scenario, Forecast
Loss Contingencies [Line Items]
Payments for legal settlements	$ 5,000,000
SEC | Disgorgement
Loss Contingencies [Line Items]
Litigation settlement, amount				4,200,000.0
SEC | Prejudgment Interest
Loss Contingencies [Line Items]
Litigation settlement, amount				753,500
SEC | Civil Penalties
Loss Contingencies [Line Items]
Litigation settlement, amount				5,100,000.0
United States Department of the Treasury
Loss Contingencies [Line Items]
Litigation settlement, amount				$ 10,000,000
Payments for legal settlements			$ 5,000,000
Auction rate securities
Loss Contingencies [Line Items]
Total amount of ARS the firm purchased and hold					92,000,000
Amount of ARS committed to purchase from clients					$ 22,800,000