Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income (loss)	$ 33,291	$ (28,369)	$ 61,192
Adjustments to reconcile net income (loss) to cash provided by operating activities, net of the effects of acquisitions:
Depreciation and amortization	160,863	140,071	19,709
Loss on disposal of fixed assets	271	134	300
Deal related compensation expense and accretion charges	153	6,728	153
Share-based compensation expense associated with equity awards	39,189	28,351	16,580
Net change in fair value of contingent and contractual liabilities	0	0	(10)
Deferred income taxes	(11,008)	(42,121)	2,736
Other (gains) losses	(111)	(279)	168
Changes in assets and liabilities
Accounts receivable and unbilled costs	(48,080)	(23,259)	(21,801)
Due from related party	25,055	(18,483)	0
Inventories	12,456	5,523	(499)
Prepaid expenses and other assets	(24,751)	(29,481)	(2,169)
Accounts payable	405	2,334	1,355
Accrued compensation and other expenses	6,785	33,250	13,233
Due to related party	(2,792)	(6,743)	0
Income taxes payable	3,008	1,984	(684)
Deferred revenue	33,075	25,645	16,670
Net cash provided by operating activities	227,809	95,285	106,933
Cash flows from investing activities:
Purchase of marketable securities	(199,841)	(100,278)	(133,212)
Proceeds from maturity of marketable securities	181,321	118,881	89,954
Purchase of fixed assets	(29,696)	(24,783)	(12,808)
Purchase of intangible assets	(1,031)	(3,962)	(174)
Acquisition of businesses, net of cash acquired	(4,606)	27,700	0
Decrease (increase) in deposits	129	(150)	55
Contingent purchase consideration	660	0	0
Collection of contingently returnable consideration	12,864	9,306	0
Change in restricted cash	(660)	0	0
Capitalized software development costs	(1,421)	(1,625)	0
Net cash (used in) provided by investing activities	(42,281)	25,089	(56,185)
Cash flows from financing activities:
Issuance of common stock under stock plans	2	1	140
Treasury stock repurchases	(89,555)	(311,850)	(51,714)
Proceeds from issuance of long-term debt, net of issuance costs	0	294,623	0
Excess tax benefit (shortfall) from share-based compensation awards	(1,045)	1,926	2,814
Net cash used in financing activities	(90,598)	(15,300)	(48,760)
Effect of exchange rate changes on cash and cash equivalents	(761)	744	829
Net increase in cash and cash equivalents	94,169	105,818	2,817
Cash and cash equivalents, beginning of year	210,711	104,893	102,076
Cash and cash equivalents, end of year	304,880	210,711	104,893
Supplemental disclosures of cash flow information:
Cash paid for interest	6,442	3,807	0
Cash paid for income taxes	49,290	50,658	29,233
Non-cash transactions:
Transfers of inventory to fixed assets	4,928	1,229	940
Additions to property, plant and equipment included in accounts payable	1,241	(1,065)	(187)
Debt issuance costs settled through the issuance of additional debt	0	5,377	0
Issuance of common stock under employee stock purchase plans	15,697	10,560	5,889
Contingent consideration related to acquisition, included in accrued other	660	0	0
Purchase consideration
Non-cash transactions:
Noncash business transaction	0	2,276,256	0
Contingently returnable consideration
Non-cash transactions:
Noncash business transaction	$ 0	$ 29,355	$ 0