Notes Payable and Long-Term Debt - Revolving Credit Facilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Aug. 31, 2014
Revolving Credit Facility
Line of Credit Facility [Line Items]
Total remaining capacity available for borrowing	$ 205,500,000
Unused borrowing capacity for asphalt purchases only	16,300,000
Prudential facility
Line of Credit Facility [Line Items]
Revolving credit maximum borrowing capacity	300,000,000
Line of credit term of facility	3 years
Total remaining capacity available for borrowing	7,500,000
A and B Senior Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit maximum borrowing capacity	350,000,000
Line of credit term of facility	5 years
Uncommitted increase option	100,000,000
Sub limit for the issuance of standby and commercial letters of credit	100,000,000
Sub limit for swing line loans	80,000,000
Outstanding letters of credit	12,200,000
Total remaining capacity available for borrowing	181,700,000
Line of credit facility outstanding amount	156,100,000
Subsidiary, One
Line of Credit Facility [Line Items]
Line of credit facility outstanding amount	13,700,000
Subsidiary, One | Line of Credit
Line of Credit Facility [Line Items]
Face amount of debt	$ 30,000,000.0	$ 40,000,000