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Acquisitions and Dispositions of Businesses (Acquisitions) (Narrative) (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($) business	Dec. 31, 2020 USD ($) business	May 31, 2020 USD ($)
Business Acquisition [Line Items]
Number of businesses acquired \| business			3
Acquisition purchase price			$ 96,800
Purchase Price Net of Cash	$ 0	$ 6,011
Goodwill expected to be deductible for income tax purposes			$ 3,200
Automotive [Member]
Business Acquisition [Line Items]
Floor plan payables	28,400
Education [Member]
Business Acquisition [Line Items]
Number of businesses acquired \| business		2	2
Education [Member] \| Kaplan International [Member]
Business Acquisition [Line Items]
Number of businesses acquired \| business		1
Education [Member] \| Supplemental Education [Member]
Business Acquisition [Line Items]
Number of businesses acquired \| business		1
Other Businesses [Member]
Business Acquisition [Line Items]
Number of businesses acquired \| business			1
Other Businesses [Member] \| Framebridge [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability				$ 50,600
Percentage of Shares Eligible to be Redeemed				20.00%
Redeemable noncontrolling interest				$ 6,000
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage				93.40%
Pinnacle Bank Term Loan [Member]
Business Acquisition [Line Items]
Loans Payable to Bank	$ 10,411		$ 10,692