Real Estate Charges - Additional Information (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2012 ft²	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2010 ft² location
Restructuring Cost And Reserve [Line Items]
Area of office space to be sub-leased (in square feet) | ft²	510,000				380,000
Consolidated number of office locations in New York | location					2
Percentage of office space subleased	90.00%
Number of office locations | location					3
Percentage of office space to be subleased in New York	70.00%
Pre-tax real estate charges as part of work force reduction		$ 998	$ 52	$ 28,424
Additional real estate charges				17,400
Real estate asset write-off charge			5,500	4,400
2010-2012 Plan [Member]
Restructuring Cost And Reserve [Line Items]
Additional real estate charges			(4,700)	17,000
New Charges [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax real estate charges as part of work force reduction			(700)	6,600
Other Charges [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax real estate charges as part of work force reduction				5,300
Additional real estate charges				400
Real estate asset write-off charge			500
2012 Plan [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax real estate charges as part of work force reduction				$ 1,300
Real estate asset write-off charge			$ 5,000