Debt - Scheduled Payments and Maturities of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Mar. 31, 2023
Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 682,301
Secured notes | Notes Payable Maturities 2023
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	200
Secured notes | Notes Payable Maturities 2024
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	9,100
Secured notes | Notes Payable Maturities 2025
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	9,700
Secured notes | Notes Payable Maturities 2026
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	10,600
Secured notes | Notes Payable Maturities 2027
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	249,000
Secured notes | Notes Payable Maturities 2028
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	17,600
Secured notes | Notes Payable Maturities 2029
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	74,750
Secured notes | Notes Payable Maturities 2030
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	9,000
Secured notes | Notes Payable Maturities 2031
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	9,600
Secured notes | Notes Payable Maturities 2032
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	10,300
Secured notes | Notes Payable Maturities Thereafter
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	282,451
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	7,250,000
Unsecured notes | Notes Payable Maturities 2023
Notes Payable, Unsecured Notes and Credit Facility
Stated interest rate of unsecured notes (as a percent)		2.85%
Unsecured notes | Notes payable 4.200 Maturities 2023
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 350,000
Stated interest rate of unsecured notes (as a percent)	4.20%
Unsecured notes | Notes Payable Maturities 2024
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 300,000
Stated interest rate of unsecured notes (as a percent)	3.50%
Unsecured notes | Notes Payable 3.450 Maturities 2025
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 525,000
Stated interest rate of unsecured notes (as a percent)	3.45%
Unsecured notes | Notes Payable 3.500 Maturities 2025
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 300,000
Stated interest rate of unsecured notes (as a percent)	3.50%
Unsecured notes | Notes Payable 2.950 Maturities 2026
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 475,000
Stated interest rate of unsecured notes (as a percent)	2.95%
Unsecured notes | Notes Payable 2.900 Maturities 2026
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 300,000
Stated interest rate of unsecured notes (as a percent)	2.90%
Unsecured notes | Notes Payable Maturities 2027
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 400,000
Stated interest rate of unsecured notes (as a percent)	3.35%
Unsecured notes | Notes Payable Maturities 2028
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 450,000
Stated interest rate of unsecured notes (as a percent)	3.20%
Unsecured notes | Notes Payable 1.900 Maturities 2028
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 400,000
Stated interest rate of unsecured notes (as a percent)	1.90%
Unsecured notes | Notes Payable Maturities 2029
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 450,000
Stated interest rate of unsecured notes (as a percent)	3.30%
Unsecured notes | Notes Payable Maturities 2030
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 700,000
Stated interest rate of unsecured notes (as a percent)	2.30%
Unsecured notes | Notes Payable Maturities 2031
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 600,000
Stated interest rate of unsecured notes (as a percent)	2.45%
Unsecured notes | Notes Payable Maturities 2032
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 700,000
Stated interest rate of unsecured notes (as a percent)	2.05%
Unsecured notes | Notes Payable Maturities 2033
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 350,000
Stated interest rate of unsecured notes (as a percent)	5.00%
Unsecured notes | Notes Payable Maturities 2046
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 350,000
Stated interest rate of unsecured notes (as a percent)	3.90%
Unsecured notes | Notes Payable Maturities 2047
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 300,000
Stated interest rate of unsecured notes (as a percent)	4.15%
Unsecured notes | Notes Payable Maturities 2048
Notes Payable, Unsecured Notes and Credit Facility
Notes Payable	$ 300,000
Stated interest rate of unsecured notes (as a percent)	4.35%