Long-Term Debt (Details) (USD $)	3 Months Ended			1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2011	Mar. 31, 2014	Mar. 31, 2016	Dec. 31, 2014	Apr. 30, 2010	May 21, 2011	Apr. 30, 1998	Dec. 31, 2013
Debt Instrument [Line Items]
Interest Rate Swap realized Gain Loss	$ 4,100,000
Senior Debentures							0.500
Potential Increase to Term Loan and Line of Credit	500,000,000
Accrued interest expense	11,700,000					9,200,000
Payments of Debt Issuance Costs	0	14,042,000
Long-term Debt	1,295,075,000					1,330,563,000
STARS [Member]
Debt Instrument [Line Items]
Payments to acquire interest in joint venture			20,000,000
Letter Of Credit Sub Facility [Member]
Debt Instrument [Line Items]
Term facility, maximum borrowing capacity	50,000,000
Multi Currency Sub Facility [Member]
Debt Instrument [Line Items]
Term facility, maximum borrowing capacity	100,000,000
Senior Note June 2021 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate percentage								7.25%
Debt instrument, face amount								400,000,000
Senior Debentures April 2028 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount									100,000,000
Contingent Credit Agreement Term Loan Facility [Member]
Debt Instrument [Line Items]
Term facility, maximum borrowing capacity	850,000,000
Repayments of Debt	10,600,000
Contingent Credit Agreement Revolving Facility [Domain]
Debt Instrument [Line Items]
Term facility, maximum borrowing capacity	550,000,000
Acquisition Notes [Member] | Non Interest Bearing Acquisition Note [Member]
Debt Instrument [Line Items]
Debt Instrument Amount Of Installment				5,000,000
Long-term Debt	4,695,000					4,623,000
Acquisition Notes [Member] | Non Interest Bearing Acquisition Note [Member] | STARS [Member]
Debt Instrument [Line Items]
Debt instrument, face amount										15,000,000
Notes Payable to Banks [Member] | Senior Note June 2021 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate percentage	7.25%
Long-term Debt	393,000,000					393,000,000
Notes Payable to Banks [Member] | Senior Debentures August 2014 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate percentage	5.70%
Notes Payable to Banks [Member] | Senior Debentures April 2028 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate percentage	7.55%								7.55%
Long-term Debt	59,645,000					59,645,000
Line of Credit [Member] | Revolving Line of Credit March 2019 [Domain]
Debt Instrument [Line Items]
Debt instrument, stated interest rate percentage	2.85%					2.41%
Long-term Debt	60,000,000					85,000,000
Bank Loans [Member] | Term Loan due March 2019 [Member] [Domain]
Debt Instrument [Line Items]
Debt instrument, stated interest rate percentage	2.77%					2.41%
Long-term Debt	775,625,000					786,250,000
Notes Payable, Other Payables [Member] | Various Interest Rate Loans [Member]
Debt Instrument [Line Items]
Long-term Debt	2,110,000					2,045,000
Swap [Member]
Debt Instrument [Line Items]
Interest Rate Swap Unrealized Gain Loss	(2,180,000)	(73,000)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	(1,400,000)
December 2017 [Domain] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Quarterly Amortization of Interest Rate Swap Notional Amount	12,500,000
Future [Member] | Acquisition Notes [Member] | Non Interest Bearing Acquisition Note [Member]
Debt Instrument [Line Items]
Debt Instrument Amount Of Installment					$ 5,000,000