Debt (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 1,507,422,000		$ 1,507,422,000		$ 1,517,559,000
Debt Instrument, Repurchased Face Amount		$ 52,000,000		$ 52,000,000
Long-term Debt, Gross	2,331,410,000		2,331,410,000		2,346,488,000
Debt Instrument, Unamortized Discount	(372,804,000)		(372,804,000)		(382,212,000)
Debt, Current	(451,184,000)		(451,184,000)		(446,717,000)
Amortization of Financing Costs	1,000,000	1,000,000	1,000,000	2,000,000
Letters of Credit Outstanding, Amount	13,000,000		13,000,000
Debt Related Costs	0	$ 7,760,000	0	7,760,000
Cash Paid for Debt Repurchased				134,000,000
Aggregate Principal of Convertible Debt, if Converted	385,000,000		385,000,000
Write off of Deferred Debt Issuance Cost				$ 1,000,000
Current Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	0		0		0
Senior Term Loan, due 2019 [Domain]
Debt Instrument [Line Items]
Long-term Debt, Gross	385,000,000		385,000,000		395,000,000
4.75% Senior Notes, due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	400,000,000		400,000,000		400,000,000
5.00% Senior Notes, due 2024 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 300,000,000		$ 300,000,000		300,000,000
Senior Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.69%		1.69%
3.75% Convertible Senior Subordinated Notes, due 2025 [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 54,886,000		$ 54,886,000		54,148,000
Long-term Debt, Gross	$ 79,966,000		$ 79,966,000		79,972,000
Convertible Debt - Conversion Rate	37.64		37.64
Debt Instrument, Unamortized Discount	$ (25,080,000)		$ (25,080,000)		(25,824,000)
treasury stock method average share price to include dilutive securities			$ 26.56
Subsequent Event - Debt Presented for Conversion			$ 64,000,000
4.00% Junior Subordinated Convertible Debentures, due 2033 [Member]
Debt Instrument [Line Items]
Long-term Debt	188,883,000		188,883,000		188,550,000
Long-term Debt, Gross	$ 304,898,000		$ 304,898,000		306,683,000
Convertible Debt - Conversion Rate	1.22		1.22
Debt Instrument, Unamortized Discount	$ (116,015,000)		$ (116,015,000)		(118,133,000)
treasury stock method average share price to include dilutive securities			$ 40.82
3.25% Convertible Senior Debentures, Due 2035 [Member]
Debt Instrument [Line Items]
Long-term Debt	182,094,000		$ 182,094,000		178,284,000
Long-term Debt, Gross	186,033,000		186,033,000		186,033,000
Debt Instrument, Unamortized Discount	(3,939,000)		$ (3,939,000)		(7,749,000)
treasury stock method average share price to include dilutive securities			$ 77.00
3.25% Convertible Senior Subordinated Exchange Debentures, due 2035 [Member]
Debt Instrument [Line Items]
Long-term Debt	218,504,000		$ 218,504,000		216,738,000
Long-term Debt, Gross	241,467,000		241,467,000		241,467,000
Debt Instrument, Unamortized Discount	(22,963,000)		(22,963,000)		(24,729,000)
3.50% Convertible Senior Subordianted Notes, Due 2044 [Member]
Debt Instrument [Line Items]
Long-term Debt	219,443,000		219,443,000		218,474,000
Long-term Debt, Gross	$ 424,250,000		$ 424,250,000		424,250,000
Convertible Debt - Conversion Rate	14.29		14.29
Debt Instrument, Unamortized Discount	$ (204,807,000)		$ (204,807,000)		(205,776,000)
3.5% Convertible senior subordinated debt [Domain]
Debt Instrument [Line Items]
Long-term Debt, Gross	424,250,000		$ 424,250,000		424,250,000
treasury stock method average share price to include dilutive securities			$ 70.00
Capitalized Lease and Other Debt Obligations [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 9,796,000		$ 9,796,000		$ 13,083,000
Minimum [Member]
Debt Instrument [Line Items]
contingent cash interest paid per stated liquidation amount			0.07
Maximum [Member]
Debt Instrument [Line Items]
contingent cash interest paid per stated liquidation amount			$ 0.15