Indebtedness: (Schedule of Credit Facilities) (Details) - USD ($)	Jun. 30, 2023	Sep. 20, 2022	Jun. 23, 2022	May 11, 2022	Jan. 28, 2022
Line of Credit Facility [Line Items]
Committed credit facilities	$ 6,300,000,000
Three Hundred Sixty-Four Day Revolving Credit Expiring January 31, 2023
Line of Credit Facility [Line Items]
Committed credit facilities	1,800,000,000
Multi-year Revolving Credit Facility, Expiring February 10, 2026
Line of Credit Facility [Line Items]
Committed credit facilities	2,000,000,000.0
Multi-year Revolving Credit Facility, Expiring September 29, 2026
Line of Credit Facility [Line Items]
Committed credit facilities	$ 2,500,000,000
Multi-year Revolving Credit Facility, Expiring September 29, 2027
Line of Credit Facility [Line Items]
Committed credit facilities		$ 2,300,000,000
Multi-year Revolving Credit Facility, Expiring February 10, 2027
Line of Credit Facility [Line Items]
Committed credit facilities					$ 1,900,000,000
Senior Unsecured Bridge Facility
Line of Credit Facility [Line Items]
Committed credit facilities			$ 11,000,000,000	$ 17,000,000,000