Leases (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Lessee, Lease, Description [Line Items]
Operating lease impairment	$ 1,100
Lease cost net of sublease income	123,748
Lessee, operating lease, lease not yet commenced, payments due	$ 17,200
Future minimum sublease payments due		$ 66,000
Rent expense for operating leases		83,400	$ 81,100
Sublease rental income		$ 15,600	$ 14,800
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	10 years
Sale Of KHE Campuses Business [Member]
Lessee, Lease, Description [Line Items]
Lease cost net of sublease income	$ 800