Income tax (benefit) provision from continuing operations (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Excess Tax Benefit from Share-based Compensation, Operating Activities	$ 758	$ 1,216	$ 1,411
Results of Operations, Income before Income Taxes [Abstract]
U.S.	(75,515)	(944)	28,245
Foreign	356,808	346,851	404,109
Income before income taxes	281,293	345,907	432,354
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current Federal Tax Expense (Benefit)	(3,966)	(3,185)	992
Current State and Local Tax Expense (Benefit)	(188)	(24)	64
Current Foreign Tax Expense (Benefit)	21,947	16,602	30,697
Current Income Tax Expense (Benefit)	17,793	13,393	31,753
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred Federal Income Tax Expense (Benefit)	(42,207)	(22,641)	14,445
Deferred State and Local Income Tax Expense (Benefit)	(1,990)	(1,562)	929
Deferred Foreign Income Tax Expense (Benefit)	(16,228)	(8,608)	(10,054)
Deferred Income Tax Expense (Benefit)	(60,425)	(32,811)	5,320
Income tax provision	(42,632)	(19,418)	37,073
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Computed expected income tax provision	98,453	121,067	151,324
State income taxes, net of federal benefits	(1,246)	(20)	686
Research and development tax credits - current year	(13,542)	(9,703)	(4,875)
Research and development tax credits - prior years	(2,511)	(1,789)	1,600
Foreign income taxed at lower than the federal rate	(114,497)	(106,939)	(116,003)
Increases related to current and prior year tax positions	14,462	19,769	16,809
Decreases related to prior year tax positions (1)	(12,103)	(33,100)	(14,581)
Withholding taxes	5,970	5,218	6,212
Change in valuation allowance	(2,482)	(14,286)	0
Intercompany prepaid tax asset amortization	(15,493)	(1,089)	0
Other	357	1,454	(4,099)
Income tax provision	$ (42,632)	$ (19,418)	$ 37,073
Increase of basic net income per share due to release of prior year tax positions	$ 0.06	$ 0.16	$ 0.07
Increase of diluted net income per share due to release of prior year tax positions	$ 0.06	$ 0.15	$ 0.07
Income Tax Holiday, Aggregate Dollar Amount	$ 6,000	$ 12,400	$ 16,800
Undistributed Earnings of Foreign Subsidiaries	3,400,000
Tax Adjustments, Settlements, and Unusual Provisions	$ 12,100
Effective Income Tax Rate Reconciliation, Other Adjustments	4.30%