Financial Commitments (Details) (USD $)	12 Months Ended				0 Months Ended	1 Months Ended					12 Months Ended			1 Months Ended		12 Months Ended			12 Months Ended		3 Months Ended			12 Months Ended									1 Months Ended			12 Months Ended				12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Swap	Oct. 20, 2010 7.625% Senior Notes due 2018	Apr. 30, 2011 7.625% Senior Notes due 2018 D	Dec. 31, 2013 7.625% Senior Notes due 2018	Dec. 31, 2012 7.625% Senior Notes due 2018	Dec. 31, 2013 Revolving credit facility	Dec. 31, 2012 Revolving credit facility	Dec. 31, 2013 Term Loan	Dec. 31, 2012 Term Loan	Aug. 03, 2011 Term Loan	Sep. 30, 2011 Equipment Financing item	Mar. 31, 2011 Equipment Financing	Dec. 31, 2013 Equipment Financing	Dec. 31, 2012 Equipment Financing	Aug. 31, 2011 Equipment Financing	Dec. 31, 2013 Transportation Equipment Loan at Fixed Rate	Dec. 31, 2012 Transportation Equipment Loan at Fixed Rate	Jun. 30, 2011 Lunda Seller Notes	Dec. 31, 2013 Lunda Seller Notes	Dec. 31, 2012 Lunda Seller Notes	Dec. 31, 2013 Transportation Equipment Loan at Variable Rate	Dec. 31, 2012 Transportation Equipment Loan at Variable Rate	Dec. 31, 2013 Land and Improvements Mortgages	Dec. 31, 2013 Land and Office Building Mortgages	Dec. 31, 2012 Land and Office Building Mortgages	Dec. 31, 2013 Land Mortgages	Dec. 31, 2013 Office Building Mortgages	Dec. 31, 2013 Office Building Mortgages at Variable Rate	Dec. 31, 2012 Office Building Mortgages at Variable Rate	Nov. 30, 2013 Land Mortgage	Jan. 31, 2012 Land Mortgage M	Dec. 31, 2012 Land Mortgage	Dec. 31, 2013 Office Building Mortgages at Fixed Rate	Dec. 31, 2012 Office Building Mortgages at Fixed Rate	Dec. 31, 2013 Other Indebtedness	Dec. 31, 2012 Other Indebtedness	Dec. 31, 2013 Equipment Financing
Debt Instrument
Long-term debt, gross							$ 300,000,000	$ 300,000,000
Unamortized debt discount					2,200,000		(1,493,000)	(1,742,000)
Total long term-debt, net of unamortized debt discount	733,884,000	737,090,000					298,507,000	298,258,000	135,000,000	120,000,000	115,000,000	152,500,000				78,055,000	80,297,000		29,582,000	30,905,000		21,750,000	21,750,000	13,363,000	14,087,000	9,404,000	6,952,000	7,599,000			3,671,000	3,915,000			1,750,000		1,111,000	22,600,000	4,918,000
Less - current maturities	(114,658,000)	(67,710,000)
Long-term debt, net	619,226,000	669,380,000
Maturity date					Nov. 01, 2018																Jul. 01, 2016
Interest rate (as a percent)							7.625%	7.625%										2.53%	6.44%	6.44%		5.00%	5.00%											0.20%	0.20%		5.62%
Imputed interest rate (as a percent)							7.75%	7.75%
Interest rate, minimum (as a percent)																2.21%	2.21%																							2.28%
Interest rate, maximum (as a percent)																3.98%	3.98%																							3.09%
Term of debt											5 years					5 years			5 years					7 years		30 years	7 years				10 years					5 years				60 months
Balloon payments																8,800,000			29,200,000					12,100,000		6,700,000			3,000,000	2,600,000	2,600,000			1,500,000		1,100,000
Description of variable rate basis																								LIBOR	LIBOR	LIBOR	LIBOR	LIBOR	LIBOR	LIBOR	Lender's Prime Rate	Lender's Prime Rate
Basis spread on variable rate (as a percent))																								2.40%	2.40%	3.00%	2.00%	2.00%	2.00%	2.00%
Negative basis spread on variable rate																															1.00%	1.00%
Interest rate at lender's prime rate									3.25%	3.25%																					3.25%	3.25%
Principal payments required under long-term debt obligations
2014	114,600,000
2015	87,400,000
2016	75,900,000
2017	5,500,000
2018	306,600,000
2019 and beyond	143,800,000
Private placement offering price (as a percent)					99.258%
Proceeds from the placement of Senior Notes					293,200,000
Debt issuance costs					4,600,000
Maximum redemption percentage of aggregate principal amount of Senior Notes (as a percent)					35.00%
Redemption price, percentage of principal amount at any time prior to November 1, 2013 (as a percent)					107.625%
Redemption price, percentage of principal amount at any time prior to November 1, 2014 (as a percent)					100.00%
Redemption price, change of control triggering event (as a percent)					101.00%
Default, minimum percentage of principal amount of Senior Notes held (as a percent)					25.00%
Minimum number of days for open Exchange Offer						30
Face amount											200,000,000		200,000,000		59,700,000			25,000,000								9,600,000								2,100,000						25,800,000
Loan amount for each loan														12,500,000
Maximum adjustment to Applicable Rate (as a percent)				0.975%
Number of equipment financing agreements														2
Number of loans obtained														2
Loans repaid during the period	$ 676,795,000	$ 626,122,000	$ 554,969,000												$ 27,400,000																		$ 1,500,000
Number of equal monthly installments of principal and interest																																		24