Equity Incentive Plans, Stock Compensation Expensed (Details) - USD ($) $ in Thousands		12 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Stock-based compensation expense [Line Items]
Share based compensation expense		$ 71,420	$ 58,596	$ 53,787
Income tax benefit		23,012	10,640	5,722
Net income effect of share-based compensation		48,408	47,956	48,065
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized		$ 134,500
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition		2 years 3 months 20 days
Inventory [Member]
Stock-based compensation expense [Line Items]
Amount of share-based compensation expense capitalized to inventory		$ 7,900	6,800	7,400
Cost of sales
Stock-based compensation expense [Line Items]
Share based compensation expense	[1]	8,252	9,010	7,340
Research and development [Member]
Stock-based compensation expense [Line Items]
Share based compensation expense		32,022	28,164	24,554
Selling, general and administrative [Member]
Stock-based compensation expense [Line Items]
Share based compensation expense		$ 31,146	$ 21,422	$ 21,893

[1] During the year ended March 31, 2016, $7.9 million of share-based compensation expense was capitalized to inventory, and $8.3 million of previously capitalized share-based compensation expense in inventory was sold. During the year ended March 31, 2015, $6.8 million of share-based compensation expense was capitalized to inventory, and $9.0 million of previously capitalized share-based compensation expense in inventory was sold. During the year ended March 31, 2014, $7.4 million of share-based compensation expense was capitalized to inventory, and $7.3 million of previously capitalized share-based compensation expense in inventory was sold.