Business Acquisitions - Allocation of Aggregate Purchase Consideration (Details) - USD ($)	Dec. 31, 2021	Jun. 04, 2021	Dec. 31, 2020	Feb. 18, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 339,209,000		$ 342,430,000		$ 320,095,000
Deferred revenue	0		(500,000)
SRFax
Business Acquisition [Line Items]
Accounts receivable				$ 194,000
Property and equipment				44,000
Goodwill				15,844,000
Accounts payables and accrued expenses				(94,000)
Deferred revenue				(519,000)
Total				24,990,000
SRFax | Trade names
Business Acquisition [Line Items]
Finite-lived intangibles				907,000
SRFax | Customer relationships
Business Acquisition [Line Items]
Finite-lived intangibles				8,235,000
SRFax | Other intangibles
Business Acquisition [Line Items]
Finite-lived intangibles				$ 379,000
SEOmoz | Discontinued Operations
Business Acquisition [Line Items]
Accounts receivable		$ 3,901,000
Prepaid expenses and other current assets		1,568,000
Property and equipment		1,838,000
Operating lease right-of-use assets		5,888,000
Goodwill	$ 41,200,000	41,213,000
Accounts payables and accrued expenses		(2,352,000)
Other current liabilities		(14,000)
Deferred revenue		(6,398,000)
Operating lease liabilities, current		(7,191,000)
Other long-term liabilities		(785,000)
Deferred tax liability		(4,936,000)
Total		66,539,000
SEOmoz | Trade names | Discontinued Operations
Business Acquisition [Line Items]
Finite-lived intangibles		7,200,000
SEOmoz | Customer relationships | Discontinued Operations
Business Acquisition [Line Items]
Finite-lived intangibles		5,000,000
SEOmoz | Other intangibles | Discontinued Operations
Business Acquisition [Line Items]
Finite-lived intangibles		$ 21,607,000
Inspired eLearning | Discontinued Operations
Business Acquisition [Line Items]
Accounts receivable			1,876,000
Prepaid expenses and other current assets			1,002,000
Property and equipment			418,000
Goodwill			13,174,000
Other long-term assets			73,000
Deferred tax asset			39,000
Accounts payables and accrued expenses			(1,878,000)
Deferred revenue			(5,935,000)
Operating lease liabilities, current			(97,000)
Total			20,472,000
Inspired eLearning | Trade names | Discontinued Operations
Business Acquisition [Line Items]
Finite-lived intangibles			2,012,000
Inspired eLearning | Customer relationships | Discontinued Operations
Business Acquisition [Line Items]
Finite-lived intangibles			3,654,000
Inspired eLearning | Other intangibles | Discontinued Operations
Business Acquisition [Line Items]
Finite-lived intangibles			$ 6,134,000