Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Income Tax [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	31.50%
Income taxes	$ 35,288	$ 41,188	$ 50,509
Transfer pricing matter tax resolution additional tax expense	$ 4,369	$ 2,169	$ 1,310
Effective Income Tax Rate Reconciliation, Percent	31.10%	27.20%	30.30%
Effective Income Tax Rate Reconciliation, Tax Holiday, Amount	$ 7,800
Reversal of dividend withholding tax due to foreign subsidiary tax holiday	0.00%	(5.10%)	0.00%
Net operating loss carryforwards	$ 0
Unrecognized tax benefits that would impact effective tax rate	2,300
Liability where a significant change in unrecognized tax benefits is reasonably possible	100
Tax settlement	8,948	$ 0	$ 0
Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle		(1,934)	$ 0
Transfer pricing issue [Member]
Income Tax [Line Items]
Transfer pricing matter tax resolution additional tax expense	$ 2,800
Effective Income Tax Rate Reconciliation, Percent	2.40%
Tax settlement	$ 8,900
Accrued Income Taxes	$ 4,500
Minimum [Member] | State And Foreign Jurisdictions [Member]
Income Tax [Line Items]
Open tax years	3 years
Maximum [Member] | State And Foreign Jurisdictions [Member]
Income Tax [Line Items]
Open tax years	6 years
Prior to Tax Cuts and Jobs Act [Member]
Income Tax [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			35.00%
Subsequent to Tax Cuts and Jobs Act [Member]
Income Tax [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%
Deferred tax liabilities			$ 0
Income taxes			4,500
Net Income [Member] | Subsequent to Tax Cuts and Jobs Act [Member]
Income Tax [Line Items]
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability			7,800
AOCI Attributable to Parent [Member]
Income Tax [Line Items]
Reclassification of Tax Effects out of Accumulated Other Comprehensive Income			(12,400)
Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle			(12,373)
Retained Earnings [Member]
Income Tax [Line Items]
Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle		$ (1,934)	$ 12,373