Segment Information, Total Assets by Segment (Details) - USD ($) $ in Thousands	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Segment Information [Abstract]
Assets	$ 3,446,439	$ 3,168,794	$ 2,948,766
Operating Segments [Member] | Research Publishing & Platforms [Member]
Segment Information [Abstract]
Assets	1,692,366	1,225,313	1,172,145
Operating Segments [Member] | Academic & Professional Learning [Member]
Segment Information [Abstract]
Assets	946,760	924,924	959,601
Operating Segments [Member] | Education Services [Member]
Segment Information [Abstract]
Assets	472,814	486,316	440,516
Corporate [Member]
Segment Information [Abstract]
Assets	$ 334,499	$ 532,241	$ 376,504