Condensed Consolidating Financial Statements - Balance Sheet (Details) - USD ($)		12 Months Ended
	May 05, 2010	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Current assets:
Cash and cash equivalents		$ 109,774,000		$ 65,004,000	$ 56,362,000	$ 57,929,000
Accounts receivable, net		92,526,000		93,168,000
Intercompany receivable		0		0
Inventories, net		147,955,000		168,879,000
Prepaid expenses and other		28,759,000		25,496,000
Total current assets		379,014,000		352,547,000
Property and equipment, net		209,311,000		241,839,000
Investment in NEC TOKIN		63,416,000		20,334,000
Investments in subsidiaries		0		0
Goodwill		40,294,000		40,294,000
Intangible assets, net		29,781,000		33,301,000
Deferred income taxes		8,593,000		8,397,000
Other assets		4,119,000		3,068,000
Long-term intercompany receivable		0		0
Total assets		734,528,000		699,780,000
Current liabilities:
Current portion of long-term debt		2,000,000		2,000,000
Accounts payable, trade		69,674,000		70,981,000
Intercompany payable		0		0
Accrued expenses		57,752,000		50,320,000
Income taxes payable		715,000		453,000
Total current liabilities		130,141,000		123,754,000
Long-term debt, less current portion		386,211,000		385,833,000
Other non-current obligations		60,131,000		74,892,000
Deferred income taxes		3,370,000		2,820,000
Long-term intercompany payable		0		0
Stockholders’ equity		154,675,000		112,481,000	164,682,000	221,884,000
Total liabilities and stockholders’ equity		734,528,000		699,780,000
Reclassifications and Eliminations
Current assets:
Cash and cash equivalents		0		0	0	0
Accounts receivable, net		0		0
Intercompany receivable		(419,633,000)		(332,957,000)
Inventories, net		0		0
Prepaid expenses and other		(2,964,000)		(2,964,000)
Total current assets		(422,597,000)		(335,921,000)
Property and equipment, net		0		0
Investment in NEC TOKIN		0		0
Investments in subsidiaries		(988,083,000)		(905,190,000)
Goodwill		0		0
Intangible assets, net		0		0
Deferred income taxes		0		0
Other assets		0		0
Long-term intercompany receivable		(103,376,000)		(110,016,000)
Total assets		(1,514,056,000)		(1,351,127,000)
Current liabilities:
Current portion of long-term debt		0		0
Accounts payable, trade		0		0
Intercompany payable		(419,633,000)		(332,957,000)
Accrued expenses		0		0
Income taxes payable		(2,964,000)		(2,964,000)
Total current liabilities		(422,597,000)		(335,921,000)
Long-term debt, less current portion		0		0
Other non-current obligations		0		0
Deferred income taxes		0		0
Long-term intercompany payable		(103,376,000)		(110,016,000)
Stockholders’ equity		(988,083,000)		(905,190,000)
Total liabilities and stockholders’ equity		(1,514,056,000)		(1,351,127,000)
Parent
Current assets:
Cash and cash equivalents		2,072,000		640,000	640,000	616,000
Accounts receivable, net		0		0
Intercompany receivable		33,613,000		30,210,000
Inventories, net		0		0
Prepaid expenses and other		3,325,000		3,325,000
Total current assets		39,010,000		34,175,000
Property and equipment, net		481,000		255,000
Investment in NEC TOKIN		0		0
Investments in subsidiaries		473,147,000		382,108,000
Goodwill		0		0
Intangible assets, net		0		0
Deferred income taxes		0		0
Other assets		0		0
Long-term intercompany receivable		63,385,000		67,500,000
Total assets		576,023,000		484,038,000
Current liabilities:
Current portion of long-term debt		0		2,000,000
Accounts payable, trade		3,000		20,000
Intercompany payable		50,051,000		280,000
Accrued expenses		18,822,000		17,305,000
Income taxes payable		0		0
Total current liabilities		68,876,000		19,605,000
Long-term debt, less current portion		352,472,000		351,952,000
Other non-current obligations		0		0
Deferred income taxes		0		0
Long-term intercompany payable		0		0
Stockholders’ equity		154,675,000		112,481,000
Total liabilities and stockholders’ equity		$ 576,023,000		484,038,000
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Percentage of ownership interest		100.00%
Current assets:
Cash and cash equivalents		$ 72,705,000		36,209,000	33,094,000	22,200,000
Accounts receivable, net		30,265,000		41,025,000
Intercompany receivable		215,183,000		132,523,000
Inventories, net		97,761,000		113,289,000
Prepaid expenses and other		14,460,000		12,161,000
Total current assets		430,374,000		335,207,000
Property and equipment, net		81,818,000		93,936,000
Investment in NEC TOKIN		63,416,000		20,334,000
Investments in subsidiaries		421,577,000		429,723,000
Goodwill		40,294,000		40,294,000
Intangible assets, net		24,665,000		27,252,000
Deferred income taxes		896,000		800,000
Other assets		3,543,000		2,452,000
Long-term intercompany receivable		38,902,000		41,428,000
Total assets		1,105,485,000		991,426,000
Current liabilities:
Current portion of long-term debt		0		0
Accounts payable, trade		34,790,000		34,618,000
Intercompany payable		294,940,000		275,498,000
Accrued expenses		19,552,000		11,807,000
Income taxes payable		2,997,000		2,983,000
Total current liabilities		352,279,000		324,906,000
Long-term debt, less current portion		31,881,000		19,881,000
Other non-current obligations		13,151,000		25,797,000
Deferred income taxes		2,236,000		2,242,000
Long-term intercompany payable		63,385,000		67,500,000
Stockholders’ equity		642,553,000		551,100,000
Total liabilities and stockholders’ equity		1,105,485,000		991,426,000
Non-Guarantor Subsidiaries
Current assets:
Cash and cash equivalents		34,997,000		28,155,000	$ 22,628,000	$ 35,113,000
Accounts receivable, net		62,261,000		52,143,000
Intercompany receivable		170,837,000		170,224,000
Inventories, net		50,194,000		55,590,000
Prepaid expenses and other		13,938,000		12,974,000
Total current assets		332,227,000		319,086,000
Property and equipment, net		127,012,000		147,648,000
Investment in NEC TOKIN		0		0
Investments in subsidiaries		93,359,000		93,359,000
Goodwill		0		0
Intangible assets, net		5,116,000		6,049,000
Deferred income taxes		7,697,000		7,597,000
Other assets		576,000		616,000
Long-term intercompany receivable		1,089,000		1,088,000
Total assets		567,076,000		575,443,000
Current liabilities:
Current portion of long-term debt		2,000,000		0
Accounts payable, trade		34,881,000		36,343,000
Intercompany payable		74,642,000		57,179,000
Accrued expenses		19,378,000		21,208,000
Income taxes payable		682,000		434,000
Total current liabilities		131,583,000		115,164,000
Long-term debt, less current portion		1,858,000		14,000,000
Other non-current obligations		46,980,000		49,095,000
Deferred income taxes		1,134,000		578,000
Long-term intercompany payable		39,991,000		42,516,000
Stockholders’ equity		345,530,000		354,090,000
Total liabilities and stockholders’ equity		$ 567,076,000		$ 575,443,000
10.5% Senior Notes
Condensed Financial Statements, Captions [Line Items]
Stated interest rate (as a percent)	10.50%	10.50%	10.50%
Percentage of capital stock	51.00%
10.5% Senior Notes | Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Percentage of capital stock	51.00%