Segments (Summary of Assets by Segment and Reconciliation of Segment Assets to Total Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Reconciliation of total segment assets to total assets
Assets	$ 9,154,162	$ 9,140,332
Operating segments
Reconciliation of total segment assets to total assets
Assets	8,372,305	8,278,491
Operating segments | Operating Assets Segment
Reconciliation of total segment assets to total assets
Assets	3,895,742	3,936,119
Operating segments | MPC Segment
Reconciliation of total segment assets to total assets
Assets	2,346,687	2,285,896
Operating segments | Seaport Segment
Reconciliation of total segment assets to total assets
Assets	946,893	924,245
Operating segments | Strategic Developments Segment
Reconciliation of total segment assets to total assets
Assets	1,182,983	1,132,231
Corporate
Reconciliation of total segment assets to total assets
Assets	$ 781,857	$ 861,841