CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
OPERATING ACTIVITIES
Net income	$ 382,575,000	$ 276,142,000	$ 264,308,000
Reconciliation of net income to net cash used in operating activities:
Depreciation, amortization, and accretion	40,530,000	38,912,000	44,941,000
Amortization on cloud computing arrangements	737,000	0	0
Loss on extinguishment of debt	0	0	447,000
Bad debt expense	3,053,000	3,498,000	2,849,000
Deferred tax (benefit) expense	(8,171,000)	2,934,000	6,939,000
Stock-based compensation	22,701,000	14,477,000	14,774,000
Excess tax benefit from stock-based compensation	(586,000)	(1,953,000)	(546,000)
Loss on disposal of long lived assets	1,019,000	698,000	277,000
Impairment of intangible assets	3,522,000	0	0
Impairment of operating lease assets and other long-lived assets	14,084,000	1,365,000	180,000
Restructuring charges	0	0	295,000
Gain on settlement of asset retirement obligations	(207,000)	(705,000)	0
Changes in operating assets and liabilities:
Trade accounts receivable, net	(33,173,000)	(10,493,000)	(16,157,000)
Inventories, net	33,378,000	(32,777,000)	8,827,000
Prepaid expenses and other current assets	(22,128,000)	2,477,000	(515,000)
Income tax receivable	1,842,000	(5,811,000)	(165,000)
Net operating lease assets and liabilities	250,000	(3,264,000)	0
Other assets	(3,103,000)	(6,558,000)	2,630,000
Trade accounts payable	79,176,000	23,312,000	26,667,000
Other accrued expenses	53,785,000	(11,112,000)	(2,792,000)
Income taxes payable	26,403,000	(6,226,000)	4,355,000
Other long-term liabilities	530,000	1,418,000	2,191,000
Net cash provided by operating activities	596,217,000	286,334,000	359,505,000
INVESTING ACTIVITIES
Purchases of property and equipment	(32,218,000)	(32,455,000)	(29,086,000)
Proceeds from sales of property and equipment	49,000	491,000	68,000
Net cash used in investing activities	(32,169,000)	(31,964,000)	(29,018,000)
FINANCING ACTIVITIES
Proceeds from short-term borrowings	9,100,000	69,336,000	162,001,000
Repayments of short-term borrowings	(9,478,000)	(69,197,000)	(161,621,000)
Debt issuance costs on short-term borrowings	0	0	(1,297,000)
Proceeds from issuance of stock	1,502,000	1,288,000	1,025,000
Proceeds from exercise of stock options	6,775,000	3,615,000	0
Repurchases of common stock	(99,147,000)	(190,405,000)	(161,395,000)
Cash paid for shares withheld for taxes	(7,432,000)	(6,148,000)	(5,328,000)
Repayments of mortgage principal	(30,901,000)	(603,000)	(578,000)
Net cash used in financing activities	(129,581,000)	(192,114,000)	(167,193,000)
Effect of foreign currency exchange rates on cash and cash equivalents	5,458,000	(2,512,000)	(3,572,000)
Net change in cash and cash equivalents	439,925,000	59,744,000	159,722,000
Cash and cash equivalents at beginning of period	649,436,000	589,692,000	429,970,000
Cash and cash equivalents at end of period	1,089,361,000	649,436,000	589,692,000
Cash paid during the period
Income taxes, net of refunds of $1,564, $5,389, and $3,824, as of March 31, 2021, 2020, and 2019, respectively	104,068,000	74,573,000	53,657,000
Interest	2,931,000	2,466,000	3,811,000
Operating leases	57,376,000	61,120,000
Non-cash investing activities
Accrued for purchases of property and equipment	2,721,000	1,171,000	1,789,000
Accrued for asset retirement obligations	1,842,000	224,000	4,706,000
Accrued for shares withheld for taxes	$ 11,679,000	$ 0	$ 0