Restructuring Charges - Roll Forward of Accrued Restructuring Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2016	$ 1,062
Restructuring charges	1,731	$ 1,642	$ 0
Payments	(1,174)
Accelerated depreciation	(409)
Accrued at December 31, 2016	1,210	1,062
Severance expenses
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2016	0
Restructuring charges	1,207
Payments	(306)
Accelerated depreciation	0
Accrued at December 31, 2016	901	0
Write-downs and retirements of fixed assets
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2016	228
Restructuring charges	409
Payments	0
Accelerated depreciation	(409)
Accrued at December 31, 2016	228	228
Lease cancellations
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2016	834
Restructuring charges	115
Payments	(868)
Accelerated depreciation	0
Accrued at December 31, 2016	$ 81	$ 834