Real Estate Charges - Additional Information (Details) ft² in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2012 ft²	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 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				380
Consolidated number of office locations in New York | location					2
Number of office locations | location					3
Percentage of office space to be subleased in New York	70.00%
Real estate asset write-off charge				$ 5,500
Additional real estate credits		$ (5,100)
Pre-tax real estate charges (credits) as part of work force reduction		17,704	$ 998	52
Restructuring charges		$ 22,800
2012 Plan [Member]
Restructuring Cost And Reserve [Line Items]
Real estate asset write-off charge				5,000
Other Charges [Member]
Restructuring Cost And Reserve [Line Items]
Real estate asset write-off charge				500
2010-2012 Plan [Member]
Restructuring Cost And Reserve [Line Items]
Additional real estate credits				(4,700)
New Charges [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax real estate charges (credits) as part of work force reduction				$ (700)