Industry Segment and Geographic Area Data (Table Text Block)	3 Months Ended	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Geographic Areas, Long-Lived Assets [Abstract]
Industry Segment and Geographic Area Data	United States   Canada   Consolidated     (Unaudited)     (All amounts are in thousands of U.S. $'s) Quarter Ended September 30, 2020             Total revenues $ 1,261,235 $ 63,673 $ 1,324,908 Depreciation and amortization, net of (gains) losses on disposal   144,222   2,193   146,415 Interest expense   39,983   542   40,525 Pretax earnings   340,200   10,819   351,019 Income tax expense   81,624   3,030   84,654 Identifiable assets   13,693,016   430,462   14,123,478               Quarter Ended September 30, 2019             Total revenues $ 1,092,762 $ 57,452 $ 1,150,214 Depreciation and amortization, net of (gains) losses on disposal   154,968   2,883   157,851 Interest expense   38,261   861   39,122 Pretax earnings   200,112   5,242   205,354 Income tax expense   47,534   1,494   49,028 Identifiable assets   12,441,917   414,285   12,856,202	United States   Canada   Consolidated     (Unaudited)     (All amounts are in thousands of U.S. $'s) Six Months Ended September 30, 2020             Total revenues $ 2,204,038 $ 108,107 $ 2,312,145 Depreciation and amortization, net of (gains) losses on disposal   312,748   5,970   318,718 Interest expense   78,637   1,409   80,046 Pretax earnings   452,149   13,188   465,337 Income tax expense   107,407   3,839   111,246 Identifiable assets   13,693,016   430,462   14,123,478               Six Months Ended September 30, 2019             Total revenues $ 2,121,336 $ 108,127 $ 2,229,463 Depreciation and amortization, net of (gains) losses on disposal   296,866   6,027   302,893 Interest expense   76,481   1,529   78,010 Pretax earnings   370,959   9,109   380,068 Income tax expense   88,648   2,672   91,320 Identifiable assets   12,441,917   414,285   12,856,202