Segment and Geographic Information Segment and Geographic Information - Disaggregated Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	$ 1,382,818	$ 1,200,181	$ 757,338
Solid Capacitors
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	935,838	771,240	575,110
Film and Electrolytic [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	206,240	201,977	182,228
Electro-magnetic, Sensors & Actuators [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	240,740	226,964	0
EMEA [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	315,535	277,898	237,437
EMEA [Member] | Solid Capacitors
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	189,992	156,169	128,617
EMEA [Member] | Film and Electrolytic [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	122,956	119,649	108,820
EMEA [Member] | Electro-magnetic, Sensors & Actuators [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	2,587	2,080	0
Americas [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	337,842	259,105	224,056
Americas [Member] | Solid Capacitors
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	297,167	227,582	202,812
Americas [Member] | Film and Electrolytic [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	30,462	22,634	21,244
Americas [Member] | Electro-magnetic, Sensors & Actuators [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	10,213	8,889	0
JPKO [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	196,101	183,191	7,081
JPKO [Member] | Solid Capacitors
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	37,496	36,698	5,834
JPKO [Member] | Film and Electrolytic [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	899	772	1,247
JPKO [Member] | Electro-magnetic, Sensors & Actuators [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	157,706	145,721	0
Asia Pacific [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	533,340	479,987	288,764
Asia Pacific [Member] | Solid Capacitors
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	411,183	350,791	237,847
Asia Pacific [Member] | Film and Electrolytic [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	51,923	58,922	50,917
Asia Pacific [Member] | Electro-magnetic, Sensors & Actuators [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	70,234	70,274	0
OEM
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	598,306	563,495	246,397
OEM | Solid Capacitors
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	290,058	262,097	162,411
OEM | Film and Electrolytic [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	81,704	86,049	83,986
OEM | Electro-magnetic, Sensors & Actuators [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	226,544	215,349	0
Distributor
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	584,618	470,324	354,639
Distributor | Solid Capacitors
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	475,190	366,569	275,591
Distributor | Film and Electrolytic [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	100,113	92,708	79,048
Distributor | Electro-magnetic, Sensors & Actuators [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	9,315	11,047	0
EMS
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	199,894	166,362	156,302
EMS | Solid Capacitors
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	170,590	142,574	137,108
EMS | Film and Electrolytic [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	24,423	23,220	19,194
EMS | Electro-magnetic, Sensors & Actuators [Member]
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	4,881	568	0
Tantalum | Solid Capacitors
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	563,255	495,114	342,184
Ceramics | Solid Capacitors
Segment and geographic information
Revenue from Contract with Customer, Excluding Assessed Tax	$ 372,583	$ 276,126	$ 232,926