The total amount of capital expenditures permitted annually.

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Maximum borrowing capacity under the letter of credit subfacility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Long Term Debt.

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Par value of debt instrument issued plus or minus a premium or a discount.

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Price expressed as a percentage of principal amount at which the Company may redeem its senior notes during a specific time period in the future.

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The maximum amount (expressed as a percentage of outstanding principal) of the Company's Senior Notes that may be redeemed during any twelve-month period.

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The price (expressed as a percentage of outstanding principal) that it would cost the Company to repurchase its Senior Notes associated with a change in control triggering event.

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Max senior secured leverage ratio to permit unlimited restricted payments under credit agreement.

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Number of shares of convertible preferred stock that have been repurchased during the period and have not been retired and are not held in treasury.

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Maximum borrowing capacity under the term loan facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity.

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Amounts drawn on term loan facility.

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Total outstanding principal amount of Senior Notes to be retired

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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The price per share of the conversion feature embedded in the debt instrument.

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Description of the conversion terms of a debt instrument which may include the conversion ratio (including all potential conversion ratios if contingently adjustable), type of debt or equity security into which the debt is convertible, the dollars of debt or the number of shares into which the instrument is convertible (or potentially convertible into), the conversion period, any contingencies associated with the conversion terms, and the existence and amount of a beneficial conversion feature.

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Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

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Face (par) amount of debt instrument at time of issuance.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Amount of debt issuance costs (for example, but not limited to, legal, accounting, broker, and regulatory fees).

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Gross amount of debt extinguished.

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The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of loans from a bank with maturities initially due after one year or beyond the normal operating cycle if longer.

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Period Type:

Long-term Debt - Textual (Details) $ / shares in Units, $ in Millions					1 Months Ended			3 Months Ended								12 Months Ended
	Mar. 24, 2016 USD ($)	Nov. 30, 2015 USD ($)	Apr. 10, 2015 USD ($)	Oct. 01, 2014 USD ($)	Jan. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Nov. 30, 2013 shares	Dec. 31, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($) shares	Dec. 31, 2012 USD ($)	Sep. 30, 2012 USD ($)	Dec. 31, 2010	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)	Dec. 31, 2011 USD ($)	Jul. 01, 2017	Feb. 23, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 01, 2015 USD ($)	Aug. 31, 2015 USD ($)	Jul. 29, 2015 USD ($)	Jul. 28, 2015	Jun. 24, 2015 USD ($)	Jun. 23, 2015 USD ($)	Jan. 29, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 22, 2014	Sep. 18, 2014 USD ($)	Nov. 29, 2013	Nov. 18, 2013 USD ($) $ / shares	Jun. 11, 2013 USD ($)	Oct. 09, 2012	Sep. 11, 2012 USD ($)	Mar. 07, 2011 USD ($)	Oct. 07, 2010 USD ($)	Dec. 01, 2009 USD ($)
Long Term Debt (Textual) [ Abstract]
Senior Notes, Face Amount																																					$ 275.0		$ 525.0
Senior secured leverage ratio maximum								1.75								1.75
Term loan facility, draw				$ 75.0
Repayments of Long-term Debt																$ 597.4	$ 302.6	$ 62.5
Loss on early extinguishment of debt								$ 2.4	$ 18.8	$ 1.2						22.4	13.2	$ 2.4
Term Loan Payable						$ 447.5		$ 443.3			$ 447.5					443.3	447.5
Senior Notes Issuance, Proceeds Used For Debt Reduction													$ 64.5
Revolver, Amounts Drawn																$ 130.0	$ 325.0
Revolver, Interest Rate at Period End						2.00%		2.30%			2.00%					2.30%	2.00%
Letters of Credit, Amount Outstanding						$ 31.8		$ 34.2			$ 31.8					$ 34.2	$ 31.8
Senior Notes, Repurchase Price, Change in Control								101.00%								101.00%
Convertible Perpetual Preferred Stock, Dividend Rate							6.50%									6.50%
Debt Issuance Cost																	20.4
Capital expenditures, permitted																											$ 350.0	$ 200.0
Financial Covenants Leverage Ratio, Maximum								4.50								4.50									4.50	4.25
2014 Credit Agreement [Member]
Long Term Debt (Textual) [ Abstract]
Term Loan Facility, Maximum Borrowing Capacity						$ 450.0		$ 450.0			$ 450.0					$ 450.0	$ 450.0
Senior secured leverage ratio maximum						4.25		1.75			4.25					1.75	4.25														1.75
Percentage Owed, Principal Outstanding, Term Loan								1.25%								1.25%
Revolving Credit Facility, Maximum Borrowing Capacity						$ 600.0		$ 600.0			$ 600.0					$ 600.0	$ 600.0
Letter of Credit, Subfacility, Maximum Borrowing Capacity						260.0		260.0			$ 260.0					260.0	260.0
Term Loan and Revolver, Basis Spread on Variable Rate											0.50%
Term Loan and Revolver, Commitment Fee Percentage											0.375%
Credit Agreement, Restriction																200.0
2013 Credit Agreement [Member]
Long Term Debt (Textual) [ Abstract]
Revolving Credit Facility, Maximum Borrowing Capacity																																			$ 600.0
Letter of Credit, Subfacility, Maximum Borrowing Capacity																																			$ 260.0
Revolving Credit Facility [Member]
Long Term Debt (Textual) [ Abstract]
Senior Notes Issuance, Proceeds Used For Debt Reduction														$ 195.0
Revolver, Amounts Drawn											$ 325.0
Term Loan Facilities [Member]
Long Term Debt (Textual) [ Abstract]
Term Loan Facility, Maximum Borrowing Capacity																									$ 500.0
Term loan facility, draw						375.0					375.0						375.0					$ 125.0
Senior Notes Issuance, Proceeds Used For Debt Reduction					$ 250.0
Term loan facility, Unused Borrowing Capacity, Amount																							$ 250.0
7.25% Senior Notes Due 2018 [Member]
Long Term Debt (Textual) [ Abstract]
Senior Notes, Face Amount																																						$ 60.0	$ 275.0
Senior Notes, Issue Price																																						103.25%
Repayments of Long-term Debt				$ 281.0								$ 30.2
Senior Notes, Redemption Price, Expressed as Percentage of Principal				103.625%
Senior Notes Issuance, Proceeds Used For Debt Reduction													33.5
Debt Instrument, Maturity Date															Oct. 01, 2018
Debt Instruments, Effective Interest Rate																																							7.50%
Senior Notes, Frequency of Periodic Payment															semiannually in arrears on April 1 and October 1 of each year.
Senior Notes, Principal Extinguished				$ 271.4
7.25% and 7.75% Senior Notes due 2018 and 2022, Respectively [Member]
Long Term Debt (Textual) [ Abstract]
Senior Notes, Face Amount																																						$ 120.0
Senior Notes, Proceeds Received From Issuance																																						122.0
Repayments of Long-term Debt												60.0	1.9
Senior Notes, Repurchase Amount, Any Twelve-Month Period																																	10.00%
Senior Notes, Redemption Price, Expressed as Percentage of Principal																																	103.00%			103.00%
Total outstanding principal amount of Senior Notes to be retired												58.1
Senior Notes Issuance, Proceeds Used For Debt Reduction													64.5						$ 45.0
8.125% Senior Notes Due 2020 [Member]
Long Term Debt (Textual) [ Abstract]
Senior Notes, Face Amount																																								$ 290.0
Senior Notes, Issue Price																																								98.327%
Repayments of Long-term Debt			$ 302.0
Senior Notes, Redemption Price, Expressed as Percentage of Principal			104.063%
Senior Notes, Stated Interest Rate																																								8.70%
Senior Notes, Principal Extinguished			$ 290.0
Senior Notes, Amount Outstanding						282.7		0.0			$ 282.7					0.0	$ 282.7
7.75% Senior Notes Due 2022 [Member]
Long Term Debt (Textual) [ Abstract]
Senior Notes, Face Amount																																						$ 60.0	$ 250.0
Senior Notes, Issue Price																																						103.50%
Repayments of Long-term Debt		$ 52.0				$ 26.0						$ 27.9
Senior Notes, Repurchase Amount, Any Twelve-Month Period						10.00%					10.00%						10.00%
Senior Notes, Redemption Price, Expressed as Percentage of Principal		103.875%				103.00%					103.00%						103.00%
Senior Notes Issuance, Proceeds Used For Debt Reduction													$ 31.0
Debt Instrument, Maturity Date															Sep. 15, 2022
Senior Notes, Stated Interest Rate																																							7.75%
Debt Instruments, Effective Interest Rate																																							7.90%
Senior Notes, Frequency of Periodic Payment															semiannually in arrears on March 15 and September 15 of each year.
Senior Notes, Principal Extinguished		$ 50.0
Senior Notes, Amount Outstanding						$ 223.7		174.3			$ 223.7					174.3	$ 223.7
Extinguishment of Debt, Amount		$ 50.0				25.1
5.75% Senior Notes Due 2024 [Member]
Long Term Debt (Textual) [ Abstract]
Senior Notes, Face Amount					$ 400.0																			$ 350.0					$ 400.0	$ 175.0		$ 175.0
Senior Notes, Issue Price					102.00%																			100.50%					102.00%	103.625%		103.625%					100.00%
Senior Notes, Proceeds From Private Offering																								$ 351.0						$ 182.0
Senior Notes, Proceeds Received From Issuance																													$ 406.0			$ 182.0					$ 270.0
Senior Notes Issuance, Proceeds Used For Debt Reduction					$ 250.0
Debt Instrument, Maturity Date													Nov. 01, 2024
Senior Notes, Stated Interest Rate																																					5.75%
Debt Instruments, Effective Interest Rate																																					5.80%
Senior Notes, Frequency of Periodic Payment													semiannually in arrears on May 1 and November 1 of each year.
Senior Notes, Amount Outstanding						447.4		1,192.6			447.4					1,192.6	447.4
5.75% Senior Notes Due 2025 [Member]
Long Term Debt (Textual) [ Abstract]
Senior Notes, Face Amount																						$ 350.0	$ 350.0
Senior Notes, Issue Price																						100.00%	100.00%
Senior Notes, Proceeds From Private Offering																						$ 344.0	$ 344.0
Senior Notes, Stated Interest Rate										5.75%
Senior Notes, Amount Outstanding						0.0		343.4			0.0					343.4	0.0
5.125% Senior Notes Due 2023 [Member]
Long Term Debt (Textual) [ Abstract]
Senior Notes, Face Amount										$ 300.0
Senior Notes, Issue Price										100.00%
Senior Notes, Proceeds Received From Issuance										$ 295.0
Senior Notes, Stated Interest Rate										5.125%
Senior Notes, Amount Outstanding						0.0		$ 294.6			0.0					$ 294.6	0.0
2.00% Convertible Senior Subordinated Notes due 2043 [Member]
Long Term Debt (Textual) [ Abstract]
Senior Notes, Face Amount						$ 320.0					$ 320.0						$ 320.0																	$ 320.0
Debt Instrument, Maturity Date							Dec. 01, 2043
Senior Notes, Stated Interest Rate																																		2.00%
Debt Instruments, Effective Interest Rate																																		6.00%
Senior Notes, Frequency of Periodic Payment							semiannually in arrears in cash on June 1 and December 1 of each year
Long-term Debt, Contingent Payment of Principal or Interest							Beginning with the six-month period starting December 1, 2018, contingent interest is payable, in addition to regular interest, if the trading price of the Convertible Notes for each of the five trading days ending two trading days prior to any six-month contingent interest period is equal to or greater than $1,200. The amount of contingent interest payable per $1,000 principal amount of the Convertible Notes in respect of any contingent interest period is equal to 0.25% of the average trading price of the Convertible Notes during the specified measurement period.
Debt Instrument, Convertible, Terms of Conversion							25.2194 shares per $1,000 principal amount									26.2583 for each $1,000 principal amount
Debt Instrument, Convertible, Conversion Price \| $ / shares								$ 38.08								$ 38.08																		$ 39.652
Debt Instrument, Convertible, Redemption Percentage							120.00%
Debt Instrument, Convertible, Threshold Trading Days												20
Debt Instrument, Convertible, Threshold Consecutive Trading Days												30 days
Debt Instrument, Redemption Price, Percentage							100.00%
Convertible Debt, Repurchase Price, Fundamental Change																																		100.00%
Capital Lease Obligations [Member] \| Minimum [Member]
Long Term Debt (Textual) [ Abstract]
Debt Instruments, Effective Interest Rate								2.00%								2.00%
Capital Lease Obligations [Member] \| Maximum [Member]
Long Term Debt (Textual) [ Abstract]
Debt Instruments, Effective Interest Rate								11.00%								11.00%
Convertible Preferred Stock [Member]
Long Term Debt (Textual) [ Abstract]
Temporary Equity, Repurchased during Period, Shares \| shares							257,110					257,110				(96,245)	257,110
London Interbank Offered Rate (LIBOR) [Member] \| 2014 Credit Agreement [Member]
Long Term Debt (Textual) [ Abstract]
Term Loan and Revolver, Basis Spread on Variable Rate																2.00%
Subsequent Event [Member] \| 7.75% Senior Notes Due 2022 [Member]
Long Term Debt (Textual) [ Abstract]
Senior Notes, Redemption Price, Expressed as Percentage of Principal																					103.875%
Senior Notes, Portion of Principal Extinguished, Commitment																					$ 50.0
Scenario, Forecast [Member]
Long Term Debt (Textual) [ Abstract]
Repayments of Long-term Debt	$ 52.0
Loss on early extinguishment of debt	$ 2.0
Financial Covenants Leverage Ratio, Maximum																				4.25