Business Acquisitions (Narrative) (Details)		6 Months Ended		12 Months Ended
	Jun. 04, 2021 USD ($)	Jun. 30, 2022 USD ($) business	Jun. 30, 2021 USD ($) business	Dec. 31, 2021 USD ($)
Business Acquisition [Line Items]
Goodwill		$ 1,603,340,000		$ 1,531,455,000
Goodwill acquired during period		81,725,000
Increase (decrease) in goodwill from adjustment under purchase accounting		$ 1,636,000
Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Number of businesses acquired | business		2	1
Fiscal 2022 Acquisitions
Business Acquisition [Line Items]
Revenue of acquiree since acquisition date		$ 7,400,000
Total consideration of transactions		107,100,000
Fair value of accounts receivable acquired		6,700,000
Amount expected to be uncollectable		0
Goodwill		81,725,000
Expected income tax deductible amount		1,200,000
Accounts receivable		6,703,000
Fiscal 2022 Acquisitions | Digital Media
Business Acquisition [Line Items]
Increase (decrease) in goodwill from adjustment under purchase accounting		1,800,000
Fiscal 2022 Acquisitions | Cybersecurity and Martech
Business Acquisition [Line Items]
Increase (decrease) in goodwill from adjustment under purchase accounting		$ (100,000)
Fiscal 2021 Acquisitions
Business Acquisition [Line Items]
Revenue of acquiree since acquisition date			$ 5,800,000
Total consideration of transactions			91,000,000
Goodwill			55,439,000
Accounts receivable			$ 3,278,000
SEOmoz Acquisition
Business Acquisition [Line Items]
Revenue of acquiree since acquisition date				3,300,000
Total consideration of transactions	$ 67,000,000
Amount expected to be uncollectable	300,000
Goodwill	41,192,000
Goodwill acquired during period				41,200,000
Expected income tax deductible amount				$ 0
Accounts receivable	3,278,000
Gross amounts due under contracts	$ 3,600,000