Acquisitions and Divestitures (Details Textual) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011 Facility	Dec. 31, 2011 Y	Dec. 31, 2010 Y
Acquisitions and Divestitures (Textual)
Amortizable intangible assets recognized				$ 11,198
Amount deducted for income tax purpose				11,198
Estimated weighted-average period intangible assets are to be amortized			20	40
Total consideration net of cash acquired	18,529		18,529	70,534
Cash paid for acquiring facilities	10,000		10,000
Gain recognized on divested assets	587	39,659
Transaction related costs			531
Cash proceeds from divestiture		61,774		42,750
Receivables		2,400
Goodwill included in book value of assets		10,300	10,300
Number of shares of common stock valued at the closing date			432,407
Closing date price			$ 42.85
Total consideration for acquired assets included in fair value of acquired assets	35,406		35,406
Number of shares issued to seller			372,992
Acquisition payment included in contingent consideration				5,000
Recognized portion of goodwill				716
Number of aggregate facilities sold		4
Aggregates [Member]
Acquisitions and Divestitures (Textual)
Number of facilities acquired	3			2
Number of facilities divested	2			3
Goodwill included in book value of assets			10,300
Concrete [Member]
Acquisitions and Divestitures (Textual)
Number of facilities acquired			10	12
Number of facilities divested	2
Amortizable intangible assets recognized	6,419		6,419
Amount deducted for income tax purpose	0		0
Goodwill included in book value of assets			0
Asphalt Mix [Member]
Acquisitions and Divestitures (Textual)
Number of facilities divested	1
Goodwill included in book value of assets			$ 0
Recycling Operation [Member]
Acquisitions and Divestitures (Textual)
Number of facilities divested	1
Rail Distribution Yard [Member]
Acquisitions and Divestitures (Textual)
Number of facilities acquired	1