Quarterly Information (unaudited) (Details) - USD ($)				3 Months Ended								12 Months Ended
	Oct. 01, 2020	Jan. 01, 2020	Oct. 01, 2019	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Gross profit				$ 23,086,000	$ 20,665,000	$ 15,897,000	$ 17,614,000	$ 23,309,000	$ 21,667,000	$ 22,959,000	$ 21,278,000	$ 77,262,000	$ 89,213,000	$ 77,743,000
Net income				$ 8,447,000	$ 521,000	$ (606,000)	$ (1,294,000)	$ 9,495,000	$ 2,141,000	$ 3,219,000	$ 334,000	$ 7,068,000	$ 15,189,000	$ 9,836,000
Earnings per share:
Basic earnings per share (in dollars per share)				$ 0.49	$ 0.03	$ (0.04)	$ (0.08)	$ 0.56	$ 0.13	$ 0.19	$ 0.02	$ 0.41	$ 0.90	$ 0.59
Diluted (in dollars per share)				$ 0.47	$ 0.03	$ (0.04)	$ (0.08)	$ 0.56	$ 0.13	$ 0.19	$ 0.02	$ 0.41	$ 0.90	$ 0.59
Revenue from External Customer [Line Items]
Revenue					$ 115,594,000	$ 106,144,000	$ 128,281,000	$ 155,399,000	$ 139,005,000	$ 149,413,000	$ 139,473,000	$ 473,107,000	$ 583,290,000	$ 515,160,000
Revenue				$ 123,088,000								473,107,000	583,290,000	515,160,000
Gain on sale of business												$ 6,064,000	$ 12,126,000	$ 0
Tuition Program Management Business
Revenue from External Customer [Line Items]
Gain on sale of business			$ 12,100,000
Alternative Fuels Division
Revenue from External Customer [Line Items]
Gain on sale of business		$ 1,100,000
IC Axon [Member]
Revenue from External Customer [Line Items]
Gain on sale of business	$ 5.0