Leases (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating lease impairment	$ 11,448	$ 1,100
Lease cost net of sublease income	135,741	123,748
Lessee, operating lease, lease not yet commenced, payments due	$ 1,900
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee, operating lease, lease not yet commenced, term of contract	1 year
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lessee, operating lease, lease not yet commenced, term of contract	2 years
Sale Of KHE Campuses Business [Member]
Lessee, Lease, Description [Line Items]
Lease cost net of sublease income	$ 800	$ 800