Acquisitions - 2016 Acquisitions summary of Fair Value of the Consideration (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	May 01, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill			$ 24,938	$ 0
Acquisition related expenses					$ 700
Imagine Easy Solutions, LLC
Business Acquisition [Line Items]
Escrow	$ 4,200
Hold-back	500
Total fair value of purchase consideration	42,300
Contingent consideration arrangements, range of outcomes, value, high	$ 18,000
Period for recognition	3 years
Contingent consideration, liability, current		$ 1,000	1,000
Total purchase consideration	$ 42,300
Imagine Easy Solutions, LLC | Achievement Of Performance Conditions
Business Acquisition [Line Items]
Contingent consideration arrangements, range of outcomes, value, high	3,000
Imagine Easy Solutions, LLC and RefME Ltd.
Business Acquisition [Line Items]
Initial cash consideration	22,007
Net working capital adjustment	200
Fair value of deferred cash consideration	17,127
Escrow	4,200
Hold-back	500
Total fair value of purchase consideration	44,034
Cash	59
Accounts receivable	2,610
Favorable lease acquired	300
Other acquired assets	212
Total acquired intangible assets	16,488
Total identifiable assets acquired	19,669
Liabilities assumed	(573)
Net identifiable assets acquired	19,096
Goodwill	24,938
Total purchase consideration	44,034
Acquisition related expenses			1,100
Imagine Easy Solutions, LLC and RefME Ltd. | Trade names
Business Acquisition [Line Items]
Total acquired intangible assets	1,840
Imagine Easy Solutions, LLC and RefME Ltd. | Domain names
Business Acquisition [Line Items]
Total acquired intangible assets	1,330
Imagine Easy Solutions, LLC and RefME Ltd. | Advertiser relationships
Business Acquisition [Line Items]
Total acquired intangible assets	6,600
Imagine Easy Solutions, LLC and RefME Ltd. | User base
Business Acquisition [Line Items]
Total acquired intangible assets	550
Imagine Easy Solutions, LLC and RefME Ltd. | Non-compete agreements
Business Acquisition [Line Items]
Total acquired intangible assets	508
Imagine Easy Solutions, LLC and RefME Ltd. | Developed technologies
Business Acquisition [Line Items]
Total acquired intangible assets	$ 5,660
RefME Ltd.
Business Acquisition [Line Items]
Initial cash consideration			$ 200
Total fair value of purchase consideration		1,800
Total purchase consideration		$ 1,800