Leases (Table Text Block)	3 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Mar. 31, 2021
Leases [Abstract]
Supplemental Balance Sheet Information Related to Leases		As of September 30, 2021     Finance   Operating   Total     (Unaudited)     (In thousands)               Buildings and improvements $ – $ 136,568 $ 136,568 Furniture and equipment   18,316   –   18,316 Rental trailers and other rental equipment   182,741   –   182,741 Rental trucks   1,325,624   –   1,325,624 Right-of-use assets, gross   1,526,681   136,568   1,663,249 Less: Accumulated depreciation   (773,691)   (51,331)   (825,022) Right-of-use assets, net$ 752,990 $ 85,237 $ 838,227	As of March 31, 2021     Finance   Operating   Total         (In thousands)                                 Buildings and improvements $ – $ 132,901 $ 132,901 Furniture and equipment   22,316   –   22,316 Rental trailers and other rental equipment   203,594   –   203,594 Rental trucks   1,494,098   –   1,494,098 Right-of-use assets, gross   1,720,008   132,901   1,852,909 Less: Accumulated depreciation   (842,970)   (40,396)   (883,366) Right-of-use assets, net$ 877,038   92,505   969,543
Summary of Weighted-average remaining lease terms and Discount rates	Finance leases       September 30,   March 31,       2021   2021   Weighted average remaining lease term (years)   3   3   Weighted average discount rate  3.6 % 3.6 %	Operating leases       September 30,   March 31,       2021   2021   Weighted average remaining lease term (years)   15.2   14.7   Weighted average discount rate  4.6 % 4.6 %
Components of Lease Expense		Six Months Ended     September 30, 2021   September 30, 2020     (Unaudited)     (In thousands)           Operating lease costs $ 16,101 $ 14,540           Finance lease cost:         Amortization of right-of-use assets $ 62,243 $ 79,259 Interest on lease liabilities   8,780   12,082 Total finance lease cost$ 71,023 $ 91,341
Maturities of Lease Liabilities		Finance leases   Operating leases     (Unaudited) Year ending September 30,   (In thousands)           2022 $ 155,818 $ 24,757 2023   129,840   22,610 2024   87,728   17,921 2025   62,633   6,045 2026   20,956   3,135 Thereafter   –   60,834 Total lease payments   456,975   135,302 Less: imputed interest   (30,820)   (50,103) Present value of lease liabilities$ 426,155 $ 85,199