Quarterly Results (Unaudited) (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2020
Mar. 31, 2019
Mar. 31, 2018
Effect of Fourth Quarter Events [Line Items]                      
Revenues $ 822,991 $ 774,261 $ 736,840 $ 696,803 $ 768,213 $ 696,238 $ 678,961 $ 638,758 $ 3,030,895 $ 2,782,170 $ 2,619,996
Cost of revenues:                      
Cost of Revenue 458,931 442,908 418,173 390,960 433,497 409,241 394,297 369,708 1,710,972 1,606,743 1,527,250
Gross Profit $ 364,060 $ 331,353 $ 318,667 $ 305,843 $ 334,716 $ 286,997 $ 284,664 $ 269,050 1,319,923 1,175,427 1,092,746
Gross Profit Percentage 44.20% 42.80% 43.20% 43.90% 43.60% 41.20% 41.90% 42.10%      
Restructuring expenses [1]                 3,143 40,708 103
Net Income (Loss) Attributable to Parent $ 123,316 $ 104,930 $ 94,769 $ 84,590 $ 108,745 $ 47,858 $ 77,457 $ 69,991 $ 407,605 $ 304,051 $ 290,915
Earnings Per Share, Basic $ 1.45 $ 1.24 $ 1.12 $ 1.00 $ 1.29 $ 0.57 $ 0.92 $ 0.83 $ 4.81 $ 3.59 $ 3.42
Earnings Per Share, Diluted $ 1.44 $ 1.23 $ 1.11 $ 0.99 $ 1.27 $ 0.56 $ 0.91 $ 0.82 $ 4.76 $ 3.56 $ 3.39
Operating Expense [Member]                      
Cost of revenues:                      
Restructuring expenses         $ 4,840 $ 26,147 $ 0 $ 0      
Service [Member]                      
Effect of Fourth Quarter Events [Line Items]                      
Revenues $ 429,399 $ 410,466 $ 399,174 $ 389,068 393,276 368,599 364,302 359,968 $ 1,628,107 $ 1,486,145 $ 1,399,363
Cost of revenues:                      
Cost of Goods and Services Sold 248,393 247,803 234,573 230,001 232,140 227,012 222,190 223,106 960,770 904,448 881,073
Product [Member]                      
Effect of Fourth Quarter Events [Line Items]                      
Revenues 393,592 363,795 337,666 307,735 374,937 327,639 314,659 278,790 1,402,788 1,296,025 1,220,633
Cost of revenues:                      
Cost of Goods and Services Sold 210,538 195,105 183,600 160,959 $ 201,357 $ 182,229 $ 172,107 $ 146,602 $ 750,202 $ 702,295 $ 646,177
Operating Expense [Member]                      
Cost of revenues:                      
Restructuring expenses $ 6 $ (448) $ (274) $ 1,389              
[1] For more information regarding our restructuring activities see Note 2 titled, "Restructuring"