Segment and Geographic Information (Products and Services) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue from External Customer [Line Items]
Revenues	$ 71,284	$ 69,588	$ 68,975	$ 66,306	$ 67,418	$ 65,605	$ 63,557	$ 59,241	$ 276,153	$ 255,821	$ 234,496
U.S.
Revenue from External Customer [Line Items]
Revenues									163,831	146,317	137,603
All other countries
Revenue from External Customer [Line Items]
Revenues									112,322	109,504	96,893
M&A
Revenue from External Customer [Line Items]
Revenues									139,917	130,471	110,456
Enterprise
Revenue from External Customer [Line Items]
Revenues									106,683	96,711	95,246
DCM
Revenue from External Customer [Line Items]
Revenues									$ 29,553	$ 28,639	$ 28,794