Borrowings Under Credit Facilities and Commercial Paper Program - Aggregate Borrowings Under Unsecured Revolving Credit Facility and Commercial Paper (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Debt Disclosure [Abstract]
Balance outstanding at quarter end	$ 354,000	$ 0	$ 354,000	$ 0
Maximum amount outstanding at any month end	1,135,000	195,000	1,135,000	195,000
Average amount outstanding (total of daily principal balances divided by days in period)	$ 754,337	$ 289,231	$ 857,328	$ 145,414
Weighted average interest rate (actual interest expense divided by average borrowings outstanding)	1.36%	0.76%	0.90%	0.76%