Real Estate Charges (Details) (USD $)	3 Months Ended	9 Months Ended		3 Months Ended	6 Months Ended	9 Months Ended		12 Months Ended		3 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Office Space Closing [Member]	Jun. 30, 2012 Office Space Closing [Member]	Sep. 30, 2012 Office Space Closing [Member]	Sep. 30, 2010 Office Space Closing [Member]	Dec. 31, 2011 Office Space Closing [Member]	Dec. 31, 2010 Office Space Closing [Member]	Sep. 30, 2012 Minimum [Member] Office Space Closing [Member]	Sep. 30, 2012 Maximum [Member] Office Space Closing [Member]
Restructuring Cost And Reserve [Line Items]
Pre-Tax real estate charges as part of work force reduction	$ 168,100,000			$ 168,100,000	$ 16,100,000				$ 101,700,000
Projected Pre-Tax real estate charges as part of workforce reduction										225,000,000	250,000,000
Area of office space to be sub-leased (in square feet)				510,000		510,000			380,000
Portion of office space to be subleased in New York				70.00%
Portion of office space subleased							75.00%
Consolidated number of office locations in New York									2
Estimated current market rental rates				131,800,000	7,100,000				76,200,000
Pre-tax real estate charges related to abandonment of office space					8,800,000
Change in estimate related to real estate charge for office space to be subleased				5,000,000	7,300,000
Real estate asset write-off charge		33,017,000	4,639,000	31,300,000	1,700,000	33,017,000			25,500,000
Real estate liability restructuring reserve [Abstract]
Balance as of beginning of period					71,164,000	71,164,000		89,793,000
Expense incurred (credit)						151,125,000		(3,506,000)
Deferred rent						22,617,000		2,288,000
Payments made						(23,188,000)		(18,696,000)
Interest accretion						826,000		1,285,000
Balance as of end of period				$ 222,544,000		$ 222,544,000		$ 71,164,000	$ 89,793,000