Borrowings Under Credit Facilities and Commercial Paper Program - Unsecured Revolving Credit Facility (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Debt Disclosure [Abstract]
Balance outstanding at quarter end	$ 0	$ 354,000	$ 0	$ 354,000
Maximum amount outstanding at any month end	0	1,135,000	205,000	1,135,000
Average amount outstanding (total of daily principal balances divided by days in period)	$ 0	$ 754,337	$ 32,735	$ 857,328
Weighted average interest rate (actual interest expense divided by average borrowings outstanding)	0.00%	1.36%	5.05%	0.90%