Debt (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Debt Instrument [Line Items]
Document Period End Date				Sep. 30, 2019
Repayments of Debt				$ 1,200,000	$ 285,200
Bank Credit Facility	$ 0			0		$ 387,061
Letters of Credit Outstanding, Amount	35,500			35,500
Line of Credit Facility, Increase (Decrease), Net	235,000		$ 55,000
Unamortized debt issuance costs	(36,070)			(36,070)		(31,762)
Total debt	3,536,296			3,536,296		3,602,078
Less: Current maturities of long-term debt	(69,527)			(69,527)		(69,896)
Total long-term debt	3,466,769			3,466,769		3,532,182
October 2018
Debt Instrument [Line Items]
Line of Credit Facility, Increase (Decrease), Net					$ 395,000
November 2020
Debt Instrument [Line Items]
Repayments of Debt				200,000
January 2022
Debt Instrument [Line Items]
Repayments of Debt				425,000
May 2024
Debt Instrument [Line Items]
Bank Credit Facility	235,000			235,000		0
April 2027
Debt Instrument [Line Items]
Repayments of Debt				46,500
December 2022
Debt Instrument [Line Items]
Repayments of Debt				32,100
Bank Credit Facility	0			0
Letters of Credit Outstanding, Amount						395,000
Term Loan [Member]
Debt Instrument [Line Items]
Repayments of Debt		$ 32,100		8,500
Line of Credit Facility, Increase (Decrease), Net		$ 17,200
June 2029 [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs	(15,500)			(15,500)
Term Loan 2022 [Member]
Debt Instrument [Line Items]
Senior Notes	0			0		641,250
Term Member 2024 [Member]
Debt Instrument [Line Items]
Repayments of Debt				8,100
Term Loan	641,875			641,875		0
Unsecured Debt
Debt Instrument [Line Items]
Unamortized pricing discounts and other	5,870			5,870		6,562
Unsecured Debt | November 2020
Debt Instrument [Line Items]
Senior Notes	0			0		200,000
Unsecured Debt | November 2021
Debt Instrument [Line Items]
Senior Notes	150,000			150,000		150,000
Unsecured Debt | January 2022
Debt Instrument [Line Items]
Senior Notes	0			0		425,000
Unsecured Debt | May 2024
Debt Instrument [Line Items]
Senior Notes	850,000			850,000		850,000
Unsecured Debt | April 2027
Debt Instrument [Line Items]
Senior Notes	153,465			153,465		200,000
Unsecured Debt | December 2027
Debt Instrument [Line Items]
Senior Notes	550,000			550,000		550,000
Unsecured Debt | June 2029 [Member]
Debt Instrument [Line Items]
Senior Notes	750,000			750,000		0
Capital Lease Obligations
Debt Instrument [Line Items]
Obligations under capital leases	191,430			191,430		211,952
Mortgages [Member]
Debt Instrument [Line Items]
Mortgage notes and other debt	$ 44,726			$ 44,726		$ 4,076