Summary of Significant Accounting Policies - Previously Reported Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary Of Significant Accounting Policies [Line Items]
Net Cash Provided by Operating Activities	$ 117,191	$ 80,057	$ 76,203
Effect of exchange rate changes on cash	1,094	(416)	(1,746)
Increase in Cash, Cash Equivalents, and Restricted Cash	16,381	(1,224)	(4,491)
Cash and Cash Equivalents, Beginning Period	6,042	7,747	12,122
Cash, Cash Equivalents, and Restricted Cash, Beginning of Period	7,885	9,109	13,600
Cash and Cash Equivalents, End of Period	11,809	6,042	7,747
Cash, Cash Equivalents, and Restricted Cash, End of Period	24,266	7,885	9,109
New Accounting Pronouncement Early Adoption Effect | ASU 2016-18
Summary Of Significant Accounting Policies [Line Items]
Net Cash Provided by Operating Activities		80,057	76,203
Effect of exchange rate changes on cash		(416)	(1,746)
Increase in Cash, Cash Equivalents, and Restricted Cash		(1,224)	(4,491)
Cash, Cash Equivalents, and Restricted Cash, Beginning of Period	7,885	9,109	13,600
Cash, Cash Equivalents, and Restricted Cash, End of Period		7,885	9,109
New Accounting Pronouncement Early Adoption Effect | ASU 2016-18 | As Reported
Summary Of Significant Accounting Policies [Line Items]
Restricted cash		(494)	116
Net Cash Provided by Operating Activities		79,563	76,319
Effect of exchange rate changes on cash		(403)	(1,746)
(Decrease) Increase in Cash and Cash Equivalents		(1,705)	(4,375)
Cash and Cash Equivalents, Beginning Period	$ 6,042	7,747	12,122
Cash and Cash Equivalents, End of Period		$ 6,042	$ 7,747