Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended
	Aug. 05, 2015	Mar. 31, 2017	Mar. 31, 2016
Business Acquisition [Line Items]
Amortization expense		$ 1,270	$ 1,822
TAS Commercial Concrete
Business Acquisition [Line Items]
Amortization expense		$ 1,300
Business combination, indefinite-lived intangible assets	$ 6,900
TAS Commercial Concrete | Contractual backlog
Business Acquisition [Line Items]
Finite-lived intangibles acquired	$ 8,700
Acquired finite-lived intangible assets, useful life	2 years
TAS Commercial Concrete | Customer Relationships
Business Acquisition [Line Items]
Finite-lived intangibles acquired	$ 18,100
Acquired finite-lived intangible assets, useful life	8 years