Special Charges and Other, Net Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		42 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Employee separation costs	$ 301		$ 9,205	$ 1,387	$ 28,821
Contract exit costs	$ 19,568		302	20,154	340
Supply commitment, period	10 years
Gain on sale of assets	$ 0		0	4,447	0
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance		$ 40,225		40,225
Charges				21,541
Payments				(9,440)
Non-cash - Other				13
Foreign exchange gains				258
Restructuring reserve, ending balance	52,597			52,597		$ 52,597
Contract Termination
Restructuring Cost and Reserve [Line Items]
Incurred cost	$ 19,500
Contract termination fee, period	5 years
Employee Severance
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance		5,474		5,474
Charges				1,387
Payments				(4,403)
Non-cash - Other				(287)
Foreign exchange gains				258
Restructuring reserve, ending balance	$ 2,429			2,429		2,429
Exit Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance		34,751		34,751
Charges				20,154
Payments				(5,037)
Non-cash - Other				300
Foreign exchange gains				0
Restructuring reserve, ending balance	50,168			50,168		50,168
Accrued Liabilities
Restructuring Reserve [Roll Forward]
Current	13,605			13,605		13,605
Other Noncurrent Liabilities
Restructuring Reserve [Roll Forward]
Non-current	38,992			38,992		38,992
Semiconductor products
Restructuring Cost and Reserve [Line Items]
Employee separation costs	300		9,200	1,400	28,800	52,500
Contract exit costs	$ 19,600		$ 300	$ 20,200	$ 300	$ 64,900
San Jose Facility | Micrel Incorporated
Restructuring Cost and Reserve [Line Items]
Proceeds from sale of property, plant, and equipment		10,000
Gain on sale of assets		$ 4,400