Long-Term Debt (Narrative) (Details) (USD $)	3 Months Ended	9 Months Ended		0 Months Ended	9 Months Ended	1 Months Ended	3 Months Ended		9 Months Ended			9 Months Ended			9 Months Ended			9 Months Ended		9 Months Ended		9 Months Ended					9 Months Ended		9 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Apr. 10, 2013 Senior Notes Due 2024 [Member]	Sep. 30, 2013 Senior Notes Due 2024 [Member]	Apr. 24, 2013 Senior Notes [Member]	Jun. 30, 2013 Senior Notes [Member]	Apr. 10, 2013 Senior Notes [Member]	Sep. 30, 2013 Senior Note Due 3/15/2015 [Member]	Apr. 24, 2013 Senior Note Due 3/15/2015 [Member]	Apr. 10, 2013 Senior Note Due 3/15/2015 [Member]	Sep. 30, 2013 Senior Note Due 4/15/2015 [Member]	Apr. 24, 2013 Senior Note Due 4/15/2015 [Member]	Apr. 10, 2013 Senior Note Due 4/15/2015 [Member]	Sep. 30, 2013 Senior Note Due 4/15/2017 [Member]	Jun. 30, 2013 Senior Note Due 4/15/2017 [Member]	Apr. 24, 2013 Senior Note Due 4/15/2017 [Member]	Sep. 30, 2013 Senior Note Due 10/1/2018 [Member]	Jun. 30, 2013 Senior Note Due 10/1/2018 [Member]	Sep. 30, 2013 Senior Note Due 4/15/2020 [Member]	Jun. 30, 2013 Senior Note Due 4/15/2020 [Member]	Sep. 30, 2013 Senior Unsecured Debt [Member] item	Sep. 30, 2013 Revolving Credit Facility [Member] item	Sep. 30, 2013 Unsecured Letter of Credit Facility [Member]	Dec. 31, 2012 Unsecured Letter of Credit Facility [Member] item	Dec. 31, 2011 Unsecured Letter of Credit Facility [Member]	Sep. 30, 2013 Unsecured Letter of Credit Facility [Member] Letter Of Credit, Extension [Member]	Dec. 31, 2012 Unsecured Letter of Credit Facility [Member] Letter Of Credit, Extension [Member]	Sep. 30, 2013 Letter Of Credit, March 2013 [Member]	Dec. 31, 2012 Letter Of Credit, March 2013 [Member]	Sep. 30, 2013 Letter Of Credit, September 2013 [Member]	Dec. 31, 2012 Letter Of Credit, September 2013 [Member]	Sep. 30, 2013 Minimum [Member] Revolving Credit Facility [Member]	Sep. 30, 2013 Maximum [Member] Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date				Apr. 10, 2013
Debt instrument, face amount				$ 750,000,000																		$ 575,000,000
Interest Rate				7.625%							6.625%			7.875%			8.25%		8.125%		8.50%
Line of credit facility maximum borrowing capacity																							750,000,000		40,000,000	190,000,000				20,000,000		20,000,000
Line of credit facility expiration date																							Nov. 03, 2016	Sep. 30, 2011			Sep. 30, 2012		Mar. 31, 2013		Sep. 30, 2013
Debt instrument, maturity date					Apr. 15, 2024				Mar. 15, 2015			Apr. 15, 2015			Apr. 15, 2017			Oct. 01, 2018		Apr. 15, 2020		Oct. 14, 2016
Issue price expressed as a percentage of principal amount (in hundredths)				100.00%
Proceeds from debt, net of issuance costs				736,900,000
Aggregate principal amount agreed to be purchased								471,300,000		700,000	194,200,000		800,000	277,100,000			225,000,000
Amount of consideration for purchase of notes								532,400,000		800,000	216,000,000		900,000	316,400,000			267,700,000
Losses on early extinguishment of debt	245,000	159,780,000	71,063,000			104,900,000	54,900,000
Loss on early extinguishment of debt, net of tax						64,900,000	34,000,000
Loss on early extinguishment of debt, net of tax (in dollars per share)						$ 0.06	$ 0.04
Repurchase of senior notes																208,800,000			17,300,000		78,500,000
Repayment of the outstanding principal balance, quarterly installments amount																						14,400,000
Interest rate margin for Base Rate borrowings, minimum (in hundredths)																						0.875%	0.50%
Interest rate margin for Base Rate borrowings, maximum (in hundredths)																						2.875%	1.50%
Interest rate margin for LIBOR borrowings, minimum (in hundredths)																						1.875%	1.50%
Interest rate margin for LIBOR borrowings, maximum (in hundredths)																						3.875%	2.50%
Initial pricing for LIBOR based borrowings (in hundredths)																						2.875%											1.00%	2.00%
Maximum permitted leverage ratio																						4.5	4.5
Line of credit facility, current borrowings																							0
Interest Rate (in thousandths)																							0.40%
Exercised extension of commitment																												$ 100,000,000
Number of letters of credit																									2