Long-Term Debt (Details)	1 Months Ended		3 Months Ended			9 Months Ended
	Mar. 31, 2016 USD ($)	Mar. 31, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Mar. 31, 2011 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Apr. 21, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 30, 2014 USD ($)	May. 21, 2011 USD ($)	Apr. 30, 2010	Apr. 30, 1998 USD ($)
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								$ 750,000,000
Accrued interest expense			$ 11,800,000			$ 11,800,000			$ 9,200,000
Payments of Debt Issuance Costs						6,452,000	$ 14,042,000
Long-term Debt			1,399,151,000			1,399,151,000			1,330,563,000
Debt Issuance Cost						6,500,000
Interest Expense, Debt			17,207,000	$ 18,398,000		48,522,000	52,547,000
Deferred Costs, Current								14,800,000
Write off of Deferred Debt Issuance Cost						1,600,000
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
Amended Credit Agreement [Member]
Debt Instrument [Line Items]
Term facility, maximum borrowing capacity								850,000,000
Senior Debentures April 2028 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount													$ 100,000,000
Contingent Credit Agreement Revolving Facility [Domain]
Debt Instrument [Line Items]
Term facility, maximum borrowing capacity								$ 550,000,000
Term Loan due March 2019 [Member] [Domain]
Debt Instrument [Line Items]
Interest Expense, Debt						400,000
Acquisition Notes [Member] | Non Interest Bearing Acquisition Note [Member]
Debt Instrument [Line Items]
Debt Instrument Amount Of Installment		$ 5,000,000
Long-term Debt			$ 4,847,000			$ 4,847,000			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] | Term Loan Due April 2020 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate percentage			1.94%			1.94%
Long-term Debt			$ 839,375,000			$ 839,375,000
Notes Payable to Banks [Member] | Senior Note June 2021 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate percentage			7.25%			7.25%
Long-term Debt			$ 393,000,000			$ 393,000,000			393,000,000
Notes Payable to Banks [Member] | Senior Debentures April 2028 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate percentage			7.55%			7.55%							7.55%
Long-term Debt			$ 59,645,000			$ 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									3.92%
Long-term Debt			$ 0			$ 0			$ 85,000,000
Line of Credit [Member] | Revolving Line of Credit April 2020 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate percentage			2.08%			2.08%
Long-term Debt			$ 100,000,000			$ 100,000,000
Bank Loans [Member] | Term Loan due March 2019 [Member] [Domain]
Debt Instrument [Line Items]
Debt instrument, stated interest rate percentage									2.41%
Long-term Debt			0			0			$ 786,250,000
Notes Payable, Other Payables [Member] | Various Interest Rate Loans [Member]
Debt Instrument [Line Items]
Long-term Debt			2,284,000			2,284,000			$ 2,045,000
Swap [Member]
Debt Instrument [Line Items]
Interest Rate Swap Unrealized Gain Loss			(2,043,000)	970,000		(3,110,000)	285,000
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax			$ (1,300,000)	$ 600,000		(1,900,000)	$ 200,000
December 2017 [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Quarterly Amortization of Interest Rate Swap Notional Amount										$ 12,500,000
December 2018 [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Quarterly Amortization of Interest Rate Swap Notional Amount										$ 25,000,000
Other Current Assets [Member]
Debt Instrument [Line Items]
Payments of Debt Issuance Costs						$ 6,100,000
Future [Member] | Acquisition Notes [Member] | Non Interest Bearing Acquisition Note [Member]
Debt Instrument [Line Items]
Debt Instrument Amount Of Installment	$ 5,000,000