Acquisitions - Grace Acquisition (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				12 Months Ended			0 Months Ended	3 Months Ended	12 Months Ended		3 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Oct. 02, 2013 Grace Pacific Corporation D	Dec. 31, 2013 Grace Pacific Corporation	Dec. 31, 2013 Grace Pacific Corporation	Dec. 31, 2012 Grace Pacific Corporation	Dec. 31, 2013 Fair Value Adjustment to Purchase Price Grace Pacific Corporation
Business Acquisition [Line Items]
Percentage of voting interest acquired								100.00%
Fair value of consideration transferred								$ 231.6
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Cash consideration								35.25
Common stock issued as consideration								196.3
Noncontrolling interest								9.1
Fair value of consideration transferred								240.7
Cash and cash equivalents								5.7
Accounts receivable								37.1
Contracts retention								9.6
Costs and estimated earnings in excess of billings on uncompleted contracts								11.7
Inventories								42.0
Property, plant and equipment								148.6
Mineral rights								18.0
Intangible assets								5.8
All other, net								10.4
Total assets acquired								288.9
Accounts payable and accrued liabilities								26.3
Billings in excess of cost and estimated earnings on uncompleted contracts								7.5
Deferred tax liability, long-term								27.1
Long-term debt, including current portion								72.7
All other, net								4.9
Total liabilities assumed								138.5
Excess of purchase price over net assets acquired	99.6				99.6	0	0	90.3
Business Acquisition, Pro Forma Information [Abstract]
Operating revenue										539.1	454.1	(0.1)
Income from continuing operations, after tax										31.7	14.8	(1.7)
Number of shares transferred in business combination								5.4
Net of debt assumed in business combination								67.6
Equity interest issued and issuable calculation basis								199.75
Business combination percent of common stock to transfer								85.00%
Weighted average of trading prices of common stock								$ 36.7859
Number of consecutive trading days								20
Holdback amount of cash portion of the acquisition price								23.5
Cash payment to shareholders' representative to cover for transaction costs								1
Acquisition related costs	0.1	2.0	1.5	1.0	4.6	6.8	0			4.6
Net earnings (loss) since acquisition									1.7
Earnings (loss) attributed to noncontrolling interest since acquisition									0.5
Construction and natural materials revenue since acquisition									54.9
Adjustments excluded from pro forma results										$ 6.9