Summary of Major Types of Costs, Cumulative Costs Incurred and Total Cost Expected Associated With Restructuring Activities (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2014
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 14,732	$ 0	$ 0
Total Expected Plan Costs	15,000			18,400
Operating expenses
Restructuring Cost and Reserve [Line Items]
Restructuring costs	14,732
Total Costs Incurred To Date	14,732
Total Expected Plan Costs	15,013
Operating expenses | Severance and related employee benefits
Restructuring Cost and Reserve [Line Items]
Restructuring costs	13,162
Total Costs Incurred To Date	13,162
Total Expected Plan Costs	13,162
Operating expenses | Contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	1,159
Total Costs Incurred To Date	1,159
Total Expected Plan Costs	1,159
Operating expenses | Other costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	411
Total Costs Incurred To Date	411
Total Expected Plan Costs	$ 692