Segment Information (Revenues Attributable to Domestic and Foreign Operations) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenue		$ 56,493	$ 54,518	$ 161,486	$ 166,662
Total Americas [Member]
Segment Reporting Information [Line Items]
Revenue		37,263	37,187	106,966	116,342
United States [Member]
Segment Reporting Information [Line Items]
Revenue		35,519	35,114	101,282	111,177
Other Americas [Member]
Segment Reporting Information [Line Items]
Revenue	[1]	1,744	2,073	5,684	5,165
EMEA [Member]
Segment Reporting Information [Line Items]
Revenue	[2],[3]	14,175	12,588	41,640	36,468
United Kingdom [Member]
Segment Reporting Information [Line Items]
Revenue		10,200	8,700	28,400	25,000
APAC [Member]
Segment Reporting Information [Line Items]
Revenue	[4]	$ 5,055	$ 4,743	$ 12,880	$ 13,852

[1] Canada, Latin America and South America

[2] Europe, the Middle East and Africa (“EMEA”)

[3] Includes revenues from the United Kingdom of $10.2 million and $8.7 million for three months ended and $28.4 million and $25.0 million for the nine months ended September 30, 2017 and 2016, respectively.

[4] Asia-Pacific (“APAC”)