Debt Narratives (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		5.10%		5.20%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		75.00%		76.00%
Bank Credit Agreement		$ 1,400,000
Letters of Credit, Maximum Borrowing Capacity		100,000		$ 175,000
Line of Credit Facility, Amount Outstanding		0		270,000
Letters of Credit Outstanding, Amount		$ 30,800
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.30%
Line of Credit Facility, Remaining Borrowing Capacity		$ 639,200
Repayments of Debt		590,100
Repayments of Long-term Debt		10,054	$ 15,071
Repayments of Other Debt		100
Gain (Loss) on Extinguishment of Debt		(581)	0
Capital Lease Obligations Incurred		13,100	7,300
Repayments of Long-term Capital Lease Obligations		8,156	7,380
Debt Issuance Costs, Line of Credit Arrangements, Net		5,200
Subsequent Event [Member]
Debt Instrument [Line Items]
Gain (Loss) on Extinguishment of Debt	$ 21,700
Term Loan Increase Decrease For Period	150,000
July 2018
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				500,000
Term Loan, Maximum Borrowing Capacity				600,000
Line of Credit Facility, Increase (Decrease), Net		10,000	15,000
Repayments of Other Debt			$ 15,000
March 2021
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		700,000
Term Loan, Maximum Borrowing Capacity		700,000
Line of Credit Facility, Amount Outstanding		30,000		0
Letters of Credit Outstanding, Amount		30,000
March 2021 | Subsequent Event [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Increase (Decrease), Net	$ 170,000
Unsecured Debt | May 2024
Debt Instrument [Line Items]
Senior Notes		850,000		$ 850,000
Unsecured Debt | July 2018
Debt Instrument [Line Items]
Repayments of Debt		310,000
Unsecured Debt | Revolving Credit Facility
Debt Instrument [Line Items]
Repayments of Debt		$ 280,000