Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary Of Significant Accounting Policies [Line Items]
Percentage of insurance coverage gap allocated for prescription drugs under Medicare Part D		50.00%
Advertising expenses		$ 900	$ 1,300	$ 1,400
Purchases of property, plant and equipment and the related current liability		200	0	200
Other Income
Summary Of Significant Accounting Policies [Line Items]
Foreign currency transaction gains and losses		(500)	100	(200)
Accounting Standards Update 2016-18
Summary Of Significant Accounting Policies [Line Items]
Restricted cash			700	800	$ 800
Prepaid Expenses and Other Current Assets | Accounting Standards Update 2016-18
Summary Of Significant Accounting Policies [Line Items]
Restricted cash		100
Other Noncurrent Assets | Accounting Standards Update 2016-18
Summary Of Significant Accounting Policies [Line Items]
Restricted cash		600	700
Subsequent Event
Summary Of Significant Accounting Policies [Line Items]
Percentage of insurance coverage gap allocated for prescription drugs under Medicare Part D	70.00%
Reserve for Product Returns
Summary Of Significant Accounting Policies [Line Items]
Provision for product revenue returns		$ 5,187	$ 4,119	$ 3,080	$ 1,059