Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2011 Year
Equipment and office facilities
Significant Accounting Policies [Line Items]
Estimated useful life, Property, Plant and Equipment, Minimum	3
Estimated useful life, Property, Plant and Equipment, Maximum	10
Buildings
Significant Accounting Policies [Line Items]
Estimated useful life, Property, Plant and Equipment, Minimum	20
Estimated useful life, Property, Plant and Equipment, Maximum	40
Software and costs for purchasing or developing software
Significant Accounting Policies [Line Items]
Estimated useful life, Software and certain costs incurred for purchasing or developing software, Minimum	3
Estimated useful life, Software and certain costs incurred for purchasing or developing software, Maximum	5