Divestitures & Assets Held for Sale (Details) - USD ($) $ in Thousands		12 Months Ended			24 Months Ended
	Oct. 01, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2021	Jan. 02, 2020	Jan. 01, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Pre-tax gain on sale of business		$ 12,126	$ 0	$ 0
Tuition Program Management Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchase price	$ 20,000
Consideration held in escrow	1,500
Additional consideration paid	100
Pre-tax gain on sale of business	12,100
Direct selling costs	100
Goodwill	$ 7,700
Alternative Fuels Division
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill		2,700
Advance payment		1,500
Accounts receivable		900
Other current assets		900
Deferred revenue		1,300
Other current liabilities		$ 200
Subsequent Event | Alternative Fuels Division
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchase price						$ 3,500	$ 6,000
Purchase price subject to achievement milestones					$ 500