Net Operating Loss Carryforwards (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
U.S. Federal and state income tax
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, amount	$ 61,302
U.S. Federal and state income tax | Minimum
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, year of expiration	2018
U.S. Federal and state income tax | Maximum
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, year of expiration	2036
Foreign
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, amount	$ 12,499
Foreign | Minimum
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, year of expiration	2018
Foreign | Maximum
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, year of expiration	2037
Indefinite
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, amount	$ 24,911
Operating loss carryforward, year of expiration	Indefinite