Leases (Components of Lease Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Finance lease cost:
Amortization of leased assets	$ 8,203	$ 7,795
Interest on lease liabilities	6,411	4,748
Sublease income	(4,173)	(4,173)
Total	$ 38,658	$ 35,190
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	well:LeaseRightOfUseAsset	well:LeaseRightOfUseAsset
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	well:LeaseRightOfUseAsset	well:LeaseRightOfUseAsset
Operating Lease, Liability, Statement of Financial Position [Extensible List]	well:LeaseLiability	well:LeaseLiability
Finance Lease, Liability, Statement of Financial Position [Extensible List]	well:LeaseLiability	well:LeaseLiability
Non-segment / Corporate
Finance lease cost:
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	well:ReceivablesAndOtherAssets	well:ReceivablesAndOtherAssets
Property operating expenses
Operating lease cost:
Lease expense	$ 23,472	$ 25,166
General and administrative expenses
Operating lease cost:
Lease expense	$ 4,745	$ 1,654