Debt and Other Financing (Narrative) (Details) - USD ($)		1 Months Ended						3 Months Ended					12 Months Ended
	Jan. 03, 2020	Dec. 31, 2019	Jul. 31, 2019	Jun. 30, 2018	Dec. 31, 2016	Oct. 31, 2016	Aug. 31, 2016	Dec. 31, 2019	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2009	Mar. 31, 2008	Jun. 30, 2003
Debt Instrument [Line Items]
Finance lease liabilities		$ 1,400,000						$ 1,400,000					$ 1,400,000			$ 1,900,000
Gain (loss) on extinguishment of debt													$ (11,600,000)	$ (700,000)	$ 0
October debt repurchase
Debt Instrument [Line Items]
Debt repurchase, premium paid						$ 6,200,000
Accrued interest paid on extinguishment of debt						1,100,000
December debt repurchase
Debt Instrument [Line Items]
Accrued interest paid on extinguishment of debt					$ 300,000
Debt repurchase discount received					1,300,000
Fourth Quarter 2018 Repurchase
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt											$ 2,100,000
Debt repurchase discount received											2,400,000			2,400,000
Payments for debt extinguishment accrued interest											700,000
Write off of debt issuance cost											300,000
2013 Notes
Debt Instrument [Line Items]
Increase in interest rate for every one-notch downgrade of long-term credit ratings below investment grade													0.25%
Maximum aggregate increase in interest rate related to downgrade of long-term credit ratings below investment grade													2.00%
2015 Facility
Debt Instrument [Line Items]
Write off of debt issuance cost										$ 2,000,000.0
2015 Facility | Subsequent Event
Debt Instrument [Line Items]
Write off of debt issuance cost	$ 7,800,000
2.375% Notes, due March 2016
Debt Instrument [Line Items]
Principal amount of debt																		$ 250,000,000.0
Interest rate, stated percentage																		2.375%
4.60% Notes, due March 2020
Debt Instrument [Line Items]
Principal amount of debt			$ 274,800,000															$ 500,000,000.0
Interest rate, stated percentage																	4.60%	4.60%
Repayments of debt							$ 50,100,000
Gain (loss) on extinguishment of debt								1,500,000	$ 8,100,000
Debt repurchase, premium paid			8,200,000
Repurchase amount			274,800,000			40,000,000.0					23,000,000.0			23,000,000.0
Accrued interest paid on extinguishment of debt			5,400,000
Make whole premium		1,400,000						1,400,000					$ 1,400,000
Debt repurchase discount received			$ 600,000
Repayments of long-term debt		112,200,000
Payments for debt extinguishment accrued interest		1,700,000
Unamortized Debt Issuance Costs		0						0			500,000		0	500,000
5.00% Notes, due March 2023
Debt Instrument [Line Items]
Principal amount of debt																		$ 500,000,000.0
Interest rate, stated percentage			5.00%														5.00%	5.00%
Repurchase amount					11,100,000						27,000,000.0			27,000,000.0
Unamortized Debt Issuance Costs		1,100,000						1,100,000			1,500,000		1,100,000	1,500,000
6.95% Notes, due March 2043
Debt Instrument [Line Items]
Principal amount of debt																		$ 250,000,000.0
Interest rate, stated percentage									6.95%								6.95%	6.95%
Repurchase amount					$ 6,200,000
Unamortized Debt Issuance Costs		2,100,000						2,100,000			2,200,000		2,100,000	2,200,000
6.50% Notes, due March 2019
Debt Instrument [Line Items]
Principal amount of debt																				$ 350,000,000.0
Interest rate, stated percentage																			6.50%	6.50%
Repayments of debt							68,100,000
Gain (loss) on extinguishment of debt												$ (2,900,000)
Repurchase amount						44,000,000.0
Repayments of long-term debt				$ 237,800,000
Payment for debt extinguishment or debt prepayment cost				6,200,000								6,200,000
Payments for debt extinguishment accrued interest				$ 4,600,000
Write off of debt issuance cost												300,000
5.75% Notes, due March 2018
Debt Instrument [Line Items]
Interest rate, stated percentage																				5.75%
Repayments of debt							108,600,000
Repurchase amount						35,200,000
4.20% Notes, due July 2018
Debt Instrument [Line Items]
Interest rate, stated percentage																					4.20%
Repayments of debt							73,800,000
Repurchase amount						$ 44,000,000.0
7.875% Senior Secured Notes, due August 2022
Debt Instrument [Line Items]
Principal amount of debt							$ 500,000,000.0
Interest rate, stated percentage							7.875%
Unamortized Debt Issuance Costs		0						0			0		0	0
6.50% Senior Secured Notes, due August 2022
Debt Instrument [Line Items]
Principal amount of debt			$ 400,000,000.0
Interest rate, stated percentage																	6.50%
Unamortized Debt Issuance Costs		$ 0						$ 0			$ 0		$ 0	$ 0
Interest Rate Swap | 6.50% Notes, due March 2019
Debt Instrument [Line Items]
Deferred gain on termination of contract												$ 3,600,000