Summary of Restructuring Charges (Detail) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1,553	$ 787	$ 1,623	$ 6,434
Termination benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,451		1,451	867
Employee and office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	102	527	172	1,202
Other incremental costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		260		865
Lease assignment charge
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 3,500