Debt and Capital Lease Obligations (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Sep. 28, 2016
Long-term Debt	$ 234,073,000	$ 225,419,000
Long-term Debt, Excluding Current Maturities	234,033,000	223,075,000
Cash payments for interest	7,352,000	2,308,000	566,000
Loss on exchange of Senior Exchangeable Notes	0	1,012,000	1,939,000
Line of Credit Facility, Current Borrowing Capacity	300,000,000
Line of Credit Facility, Maximum Borrowing Capacity	350,000,000
Performance bonds under credit facility	17,000,000
Line of Credit Facility, Remaining Borrowing Capacity	199,000,000
Performance Bonds	22,900,000
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	150,000,000
Long-term Debt	150,000,000	150,000,000
Line of Credit [Member]
Debt Instrument [Line Items]
Long-term Debt	84,000,000	73,000,000
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Long-term Debt	73,000	132,000
Other Debt Obligations [Member]
Debt Instrument [Line Items]
Long-term Debt	0	2,287,000
Short-term Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	40,000	2,344,000
senior notes series a [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	75,000,000
Debt Instrument, Maturity Date	Sep. 30, 2021
Debt Instrument, Interest Rate, Effective Percentage	4.01%
Senior Notes Series B [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 75,000,000
Debt Instrument, Maturity Date	Sep. 30, 2023
Debt Instrument, Interest Rate, Effective Percentage	4.11%
Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.50%
Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.25%