Fair Value Measurements Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, Long-term and Short-term, Combined Amount	$ 281,232	$ 274,655
Goodwill impairment	0	2,071	0
Goodwill	238,581	203,923	192,046
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, Long-term and Short-term, Combined Amount	281,232	274,655
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, Long-term and Short-term, Combined Amount	109,024	107,093
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, Long-term and Short-term, Combined Amount	172,208	167,562
Portion at Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, Long-term and Short-term, Combined Amount	309,392	303,295
Portion at Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, Long-term and Short-term, Combined Amount	145,188	147,822
Portion at Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt, Long-term and Short-term, Combined Amount	164,204	155,473
VT composites [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill impairment		2,100
Goodwill		16,800
VT composites [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill impairment		$ 2,100