Acquisitions - Intangibles (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2014
Noncompete agreements
Intangibles
Amortization period	4 years
Trynex | Customer Relationships
Intangibles
Acquired intangible assets, finite lived	8,820
Amortization period	19 years 6 months
Trynex | Patents
Intangibles
Acquired intangible assets, finite lived	1,320
Amortization period	17 years
Trynex | Trademark
Intangibles
Acquired intangible assets, finite lived	2,359
Amortization period	25 years
Trynex | Goodwill
Intangibles
Amortization period	15 years
Henderson
Intangibles
Goodwill expected to be deductible	4,218	4,218
Amortization period		10 years 3 months 18 days
Henderson | Trademark
Intangibles
Acquired intangible assets, indefinite lived		3,600
Henderson | Customer Relationships
Intangibles
Acquired intangible assets, finite lived		8,300
Amortization period		15 years
Henderson | Patents
Intangibles
Acquired intangible assets, finite lived		3,200
Amortization period		10 years
Henderson | Noncompete agreements
Intangibles
Acquired intangible assets, finite lived		2,090
Amortization period		4 years
Henderson | Backlog
Intangibles
Acquired intangible assets, finite lived		$ 200
Amortization period		6 months