Description of Business and Summary of Significant Accounting Policies (Revenues by product line and geographic area) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Revenue from External Customer [Line Items]
Total	$ 44,503	$ 42,713	$ 36,238	$ 35,804	$ 37,376	$ 42,030	$ 38,546	$ 29,224	$ 159,258		$ 147,176		$ 121,882
China [Member]
Revenue from External Customer [Line Items]
Total									74,054		43,187		30,835
Germany [Member]
Revenue from External Customer [Line Items]
Total									25,119		26,253		27,579
United States [Member]
Revenue from External Customer [Line Items]
Total									26,473		29,723		22,248
All other countries [Member]
Revenue from External Customer [Line Items]
Total									33,612	[1]	48,013	[1]	41,220	[1]
Ultracapacitors [Member]
Revenue from External Customer [Line Items]
Total									95,953		86,836		68,501
High-Voltage Capacitors [Member]
Revenue from External Customer [Line Items]
Total									45,574		42,309		35,708
Microelectronic Products [Member]
Revenue from External Customer [Line Items]
Total									$ 17,731		$ 18,031		$ 17,673

[1] Revenue from external customers located in countries included in “All other countries” do not individually compromise more than 10% of total revenues for any of the years presented.