Merger with Capella Education Company - Goodwill (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Aug. 01, 2018	Dec. 31, 2017
Business Combination Segment Allocation [Line Items]
Goodwill	$ 730,729		$ 20,744
Strayer
Business Combination Segment Allocation [Line Items]
Goodwill	337,381		$ 6,800
Capella
Business Combination Segment Allocation [Line Items]
Goodwill	$ 393,348
Capella Merger
Business Combination Segment Allocation [Line Items]
Goodwill		$ 723,929
Capella Merger | Strayer
Business Combination Segment Allocation [Line Items]
Goodwill		330,600
Capella Merger | Capella
Business Combination Segment Allocation [Line Items]
Goodwill		$ 393,300