Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Jul. 31, 2012	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]
U.S. federal income tax rate				35.00%
Non-U.S. jurisdiction income tax rate	24.00%	26.00%		23.00%
Foreign currency transaction gain			$ 5.1	$ 6.3
Current exchange rate between GBP and US dollars			1.55	1.63	1.55
Gain (loss) on foreign exchange					6.4
Impact of new accounting guide lines after tax				$ 25.8
Percentage of reduction on stockholders' equity				1.00%
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property, equipment and leasehold improvements, estimated useful lives				3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property, equipment and leasehold improvements, estimated useful lives				30 years
Software | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property, equipment and leasehold improvements, estimated useful lives				5 years
Software | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property, equipment and leasehold improvements, estimated useful lives				7 years