Acquisitions (Narrative) (Details) (USD $)	0 Months Ended	12 Months Ended	1 Months Ended	0 Months Ended	3 Months Ended	0 Months Ended
	Nov. 09, 2012	Dec. 31, 2013	Mar. 31, 2014	Jun. 02, 2014	Mar. 31, 2015	Nov. 07, 2014	Nov. 08, 2014	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill		$ 32,724,000			$ 80,310,000			$ 80,848,000
Engage Pty Ltd. [Member]
Business Acquisition [Line Items]
Business acquisition, acquisition date	Nov. 09, 2012
Acquisition costs incurred to acquire entity		500,000
Assets acquired liabilities assumed, net	800,000
Potential earn-out consideration	1,700,000				300,000
Engage [Member]
Business Acquisition [Line Items]
Total consideration transferred	10,600,000
NexGraph, LLC [Member]
Business Acquisition [Line Items]
Business acquisition, acquisition date			Mar. 11, 2014
Acquired Intangible Assets Amount			500,000
Intangible assets			100,000
Goodwill			400,000
Synchronite, LLC [Member]
Business Acquisition [Line Items]
Business acquisition, acquisition date				Jun. 02, 2014
Total consideration transferred				4,100,000
Acquisition costs incurred to acquire entity					400,000
Assets acquired liabilities assumed, net				45,000
Potential earn-out consideration				1,800,000
Intangible assets				1,451,000	1,450,000
Goodwill					2,700,000
Contact At Once! [Member]
Business Acquisition [Line Items]
Business acquisition, acquisition date						Nov. 07, 2014
Total consideration transferred							67,000,000
Acquired intangible asset, aggregate cash consideration						66,998,000
Potential earn-out consideration						4,200,000
Intangible assets						20,400,000
Goodwill						45,064,000
Cash payment						42,800,000
Consideration transferred, shares						$ 20,000,000