INCOME TAXES (Details) - USD ($)		12 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Current:
Federal		$ 15,702,000	$ 26,938,000	$ 28,859,000
State		1,934,000	2,685,000	1,263,000
Foreign		4,644,000	4,253,000	4,384,000
Total current provision for income taxes		22,280,000	33,876,000	34,506,000
Deferred:
Federal		(7,767,000)	(1,148,000)	(4,675,000)
State		(1,103,000)	(1,353,000)	(629,000)
Foreign		374,000	1,575,000	(480,000)
Total deferred benefit for income taxes		(8,496,000)	(926,000)	(5,784,000)
Income tax expense		13,784,000	32,950,000	28,722,000
Components of income before income taxes
United States		42,184,000	83,583,000	85,231,000
Foreign		39,992,000	61,668,000	55,908,000
Income before income taxes		82,176,000	145,251,000	141,139,000
Reconciliation between statutory federal income taxes and income tax expense
Tax expense at statutory rate		28,762,000	50,838,000	49,399,000
Foreign operations taxed at different rates		(9,478,000)	(15,839,000)	(16,175,000)
State taxes, net of federal benefit		831,000	1,331,000	634,000
Research and development credit		(3,133,000)	(2,460,000)	(1,805,000)
Unwind of stock based compensation cost sharing		(2,855,000)	0	0
Other, net		(343,000)	(920,000)	(3,331,000)
Income tax expense		$ 13,784,000	$ 32,950,000	$ 28,722,000
Effective tax rate		16.80%	22.70%	20.40%
Indefinitely reinvested foreign earnings		$ 657,300,000
Components of Deferred Tax Assets
Accruals and other reserves		5,896,000	$ 5,100,000
Deferred Compensation		3,750,000	2,066,000
Net operating loss carry forward		2,955,000	3,043,000
Stock compensation		12,561,000	9,865,000
Prepaid cost sharing		6,199,000	0
Tax credits		3,642,000	3,406,000
Other deferred tax assets		1,684,000	2,903,000
Valuation allowance		(1,962,000)	(1,940,000)
Total deferred tax assets		34,725,000	24,443,000
Components of Deferred Tax Liabilities
Deferred gains on sales of properties		(1,761,000)	(1,756,000)
Unremitted earnings of certain subsidiaries		(4,481,000)	(3,064,000)
Fixed asset depreciation		(4,846,000)	(4,650,000)
Total deferred tax liabilities		(11,088,000)	(9,470,000)
Net deferred tax assets	[1]	23,637,000	14,973,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period		12,821,000	12,571,000	$ 11,072,000
Increase (decrease) of unrecognized tax benefits related to prior years		(598,000)	(244,000)	641,000
Increase of unrecognized tax benefits related to the current year		2,252,000	1,908,000	2,427,000
Reductions to unrecognized tax benefits related to settlements with taxing authorities		(149,000)	0	0
Reductions to unrecognized tax benefits related to lapse of applicable statute of limitations		(1,634,000)	(1,414,000)	(1,569,000)
Balance at end of period		12,692,000	12,821,000	$ 12,571,000
Unrecognized Tax Benefits, Interest on Income Taxes Accrued		1,600,000	1,800,000
Accrued penalties related to unrecognized tax benefits		$ 0	$ 0

[1] The Company's deferred tax assets for the fiscal year ending March 31, 2016 and the long-term portion of the Company's deferred tax assets for the fiscal year ending March 31, 2015, are included as a component of other assets on the consolidated balance sheets.