Real Estate Charges (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Sep. 30, 2012 sqft	Dec. 31, 2013	Dec. 31, 2010 sqft Location
Restructuring Cost and Reserve [Line Items]
Area of office space to be sub-leased (in square feet)		510,000		380,000
Portion of office space subleased (in hundredths)		70.00%		90.00%
Consolidated number of office locations in New York				2
Number of Locations				3
Portion of office space to be subleased in New York (in hundredths)		70.00%
Real estate charges	$ 1,942,000
Real estate charges relating to acquistion	1,900,000
Real estate charges relating to accelerated amortization of leasehold improvements	1,700,000
Change in estimate related to real estate charge	1,700,000
Real estate liability restructuring reserve [Abstract]
Balance as of beginning of period	199,527,000		238,784,000
(Credit) expense incurred	(1,496,000)		18,371,000
Deferred rent	0		326,000
Payments made	(12,208,000)		(62,627,000)
Interest accretion	1,252,000		4,673,000
Balance as of end of period	$ 187,075,000		$ 199,527,000