Debt and Lease Obligations (Senior Credit Facility) (Details)		3 Months Ended	9 Months Ended		12 Months Ended
	Oct. 14, 2015	Dec. 31, 2015 USD ($)	Oct. 13, 2015	Sep. 30, 2015	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Oct. 04, 2013 USD ($)
Line of Credit Facility [Line Items]
Domestic subsidiaries unconditional guarantee					100.00%
Repayments of Long-term Debt					$ 45,000,000	$ 40,000,000	$ 25,000,000
Term Loan Facility
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount								$ 400,000,000
Debt Instrument Amended Maturity Period by Two Years					2 years
Repayments of Long-term Debt					$ 45,000,000	40,000,000	$ 25,000,000
Credit Facilities Scheduled Repayments Due in Next four Quarters		$ 15,000,000			15,000,000
Credit Facilities Scheduled Repayment Due in Two Years		60,000,000			60,000,000
Credit Facilities Scheduled Repayment Due in Three Years		60,000,000			60,000,000
Credit Facilities Scheduled Repayment Due in Four Years		45,000,000			45,000,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity								$ 1,000,000,000
Credit Agreement Maximum Borrowing Capacity in Additional Borrowings					400,000,000
Line of Credit Facility, Amount Outstanding		0			0	0
Line of Credit Facility, Current Borrowing Capacity		$ 894,800,000			$ 894,800,000	923,200,000
Senior Credit Facility
Line of Credit Facility [Line Items]
Debt Instrument Amended Maturity Period by Two Years	2 years
Amended Debt Instrument Maturity Date	Oct. 14, 2020
Line of Credit Facility, Commitment Fee Percentage		0.15%	0.175%		0.15%
Debt Instrument, Maximum Permitted Leverage Ratio, Debt to Total Consolidated EBITDA				3.25
Debt instrument, Amended Maximum Permitted Leverage Ratio, Debt to Total Consolidated EBITDA	3.5
Letters of Credit Outstanding, Amount		$ 105,200,000			$ 105,200,000	$ 76,800,000