Goodwill and Intangible Assets Amortization Expense (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Amortization Expense [Line Items]
Amortization of Intangible Assets	$ 9,422	$ 5,007	$ 3,760	[1]
Charge from impairment of certain intangible assets	$ 0	$ 0	$ 674

[1] (a) During the year ended December 31, 2010, the Company incurred a charge of $674 from the impairment of certain intangible assets that originated from its acquisition of World Tax Services US in July 2008. World Tax Service US operated as part of the Financial Advisory segment. The impairment resulted from the departure of the two managing directors who ran the practice and associated staff in March 2010.