Summary of Major Types of Costs, Cumulative Costs Incurred and Total Cost Expected Associated With Restructuring Activities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 45	$ 279	$ 14,732
Cumulative Costs Incurred To Date	15,056
Total Expected Plan Costs	15,056
Operating expenses
Restructuring Cost and Reserve [Line Items]
Restructuring costs	45	279	14,732
Severance and related employee benefits
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	0
Cumulative Costs Incurred To Date	13,162
Total Expected Plan Costs	13,162
Severance and related employee benefits | Operating expenses
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	0	13,162
Contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	0
Cumulative Costs Incurred To Date	1,159
Total Expected Plan Costs	1,159
Contract termination costs | Operating expenses
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	0	1,159
Other costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	45	279
Cumulative Costs Incurred To Date	735
Total Expected Plan Costs	735
Other costs | Operating expenses
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 45	$ 279	$ 411