Segments (Summary of Assets by Segment and Reconciliation of Segment Assets to Total Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Reconciliation of total segment assets to total assets
Assets	$ 9,514,913	$ 9,140,332
Operating segments
Reconciliation of total segment assets to total assets
Assets	8,757,098	8,278,491
Operating segments | Operating Assets
Reconciliation of total segment assets to total assets
Assets	3,758,022	3,936,119
Operating segments | MPC Segment
Reconciliation of total segment assets to total assets
Assets	2,487,183	2,285,896
Operating segments | Seaport Segment
Reconciliation of total segment assets to total assets
Assets	985,069	924,245
Operating segments | Strategic Developments Segment
Reconciliation of total segment assets to total assets
Assets	1,526,824	1,132,231
Corporate
Reconciliation of total segment assets to total assets
Assets	$ 757,815	$ 861,841