Cash Equivalents and Marketable Securities - Additional Information (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended
		Dec. 31, 2009	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Jan. 01, 2018
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents			$ 47,322	$ 24,300	$ 53,039
Cash, cash equivalents, and short-term investments			28,485		31,813
Money market funds, at carrying value					31,200
Cash					21,800
Percentage of outstanding shares owned at time of investment		16.60%
Statutory resale restriction expiry period		4 months
Effect of new accounting principle	[1]					$ (4,060)
Unrealized gains (losses)			(103)	$ 26
Other Expense [Member]
Cash and Cash Equivalents [Line Items]
Unrealized gains (losses)			(100)
Accounting Standards Update 2016-01 [Member]
Cash and Cash Equivalents [Line Items]
Effect of new accounting principle						$ 500
Common Shares of Co Two Solution [Member]
Cash and Cash Equivalents [Line Items]
Number of common shares fair value		10,000,000
Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents			28,001		$ 31,225
Cash, cash equivalents, and short-term investments			28,000
Cash [Member]
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents, and short-term investments			$ 19,300

[1] (1) Cumulative effect of change in accounting principles includes: Accounting Standards Update 2014-9 (Topic 606), of $4.1 million and Accounting Standards Update 2016-01 (Subtopic 825-10), of $0.5 million.