Related Party Transations (Table Text Block)	3 Months Ended
	Jun. 30, 2020
Related Party Revenue [Abstract]
Related Party Revenue	Quarter Ended June 30,     2020   2019     (Unaudited)     (In thousands) U-Haul management fee revenue from Blackwater $ 6,148 $ 6,249 U-Haul management fee revenue from Mercury   1,199   907   $ 7,347 $ 7,156
Related Party costs and expenses	Quarter Ended June 30,     2020   2019     (Unaudited)     (In thousands) U-Haul lease expenses to Blackwater $ 657 $ 658 U-Haul commission expenses to Blackwater   15,332   17,202   $ 15,989 $ 17,860
Related party assets	June 30,   March 31,     2020   2020     (Unaudited)         (In thousands) U-Haul receivable from Blackwater $ 22,897 $ 25,293 U-Haul receivable from Mercury   5,555   9,893 Other (a)   (19,046)   (402)   $ 9,406 $ 34,784 (a)       Timing differences for intercompany balances with insurance subsidiaries resulting from the three-month difference in reporting periods. Our credit balance as of June 30, 2020, was due to a timing difference for a dividend paid by Oxford to AMERCO of $ 18.6 million.