Borrowings (Narrative) (Details) (USD $)	12 Months Ended					3 Months Ended	12 Months Ended		12 Months Ended				3 Months Ended			1 Months Ended	12 Months Ended								1 Months Ended			1 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Securitization Program [Member]	Dec. 31, 2010 Securitization Program [Member]	Jun. 26, 2011 6.875% Senior Subordinated Notes Due 2019 [Member]	Dec. 31, 2011 6.875% Senior Subordinated Notes Due 2019 [Member]	Jun. 13, 2011 6.875% Senior Subordinated Notes Due 2019 [Member]	Dec. 31, 2011 Term Loan [Member]	Dec. 31, 2011 3.875% Convertible Senior Subordinated Notes Due 2017 [Member]	Mar. 31, 2011 Senior Credit Facility, Term Loan Facility, At An Average Rate Of 1.31%, Due 10/1/2012 [Member]	Dec. 31, 2010 Senior Credit Facility, Term Loan Facility, At An Average Rate Of 1.31%, Due 10/1/2012 [Member]	Mar. 27, 2011 2004 Senior Notes [Member]	Dec. 31, 2011 2004 Senior Notes [Member]	Dec. 31, 2011 London Interbank Offered Rate [Member]	Mar. 31, 2011 Incremental Facility [Member]	Dec. 31, 2011 Incremental Facility [Member]	Dec. 31, 2011 Extension Of Senior Credit Facility [Member]	Mar. 31, 2011 Extension Of Senior Credit Facility [Member]	Mar. 27, 2011 Revolving Credit Facility [Member]	Dec. 31, 2011 Revolving Credit Facility [Member] Standby Letters Of Credit [Member]	Dec. 31, 2011 Federal Funds Rate [Member]	Dec. 31, 2011 Prime Rate [Member]	Dec. 31, 2011 Maximum [Member] London Interbank Offered Rate [Member]	Mar. 31, 2011 Maximum [Member] Extension Of Senior Credit Facility [Member]	Dec. 31, 2011 Maximum [Member] Federal Funds Rate [Member]	Dec. 31, 2011 Minimum [Member] London Interbank Offered Rate [Member]	Mar. 31, 2011 Minimum [Member] Extension Of Senior Credit Facility [Member]	Dec. 31, 2011 Minimum [Member] Federal Funds Rate [Member]	Dec. 31, 2011 Minimum [Member] Libor [Member]
Line of Credit Facility [Line Items]
6.875% Senior Subordinated Notes due 2019							$ 250,000,000
Principal amount of senior subordinated notes issued	400,000,000	400,000,000						250,000,000		400,000,000
Interest rate							6.875%			3.875%														2.625%
Transaction fees							3,700,000											300,000
Prepayment of debt													165,800,000
Loss on extinguishments of debt	(15,413,000)	(46,630,000)				800,000							700,000
Percent of redemption price to principal amount any time on or after June 1, 2015							103.438%
Declining percent of redemption price to principal amount on June1, 2017							100.00%
Percent of redemption price to principal amount on redemption at any time prior to June 1, 2015							100.00%
Prepayment to holders, make-whole amount and accrued and unpaid interest													13,900,000
Percent of principal amount of notes subject to redemption							1.00%
Percent of redemption price of the principal amount of the notes redeemed, plus accrued and unpaid interest							106.875%
Percent of principal amount of notes redeemable							35.00%
Line of credit facility				4,700,000	29,700,000						36,100,000	36,123,000		150,000,000			375,000,000		33,700,000	165,000,000	3,000,000
Amount available in committed financing under the revolving credit facility	397,000,000
Repayment of borrowings under senior credit facilities									125,000,000							80,000,000
Basis spread							0.50%								0.375%							0.50%	1.00%							2.25%
Additional margin over libor plus basis spread																								2.75%		1.75%	1.50%		0.50%
Additional borrowings on convertible notes																100,000,000
Maximum amount available for borrowing				42,500,000																400,000,000
Commitment fee percent	0.375%																								0.50%			0.375%
Number of trading days										20
Number of consecutive trading days										30
Percentage of conversion price of applicable trading day										130.00%
Number of business days										5
Principal amount of Convertible Notes										1,000
Percentage of the product of the last reported sale price of the common stock										98.00%
Convertible notes, earliest date	May 1, 2017
Convertible notes, latest date	July 28, 2017
Carrying amount of long-term debt	954,809,000	813,409,000
Fair value of long-term debt	1,122,500,000
Consideration received from the sale of undivided interests in receivables	75,000,000
Debt Instrument Maturity Dates							2019			2017							October 1, 2014
Debt instrument maturity date							2019			2017							October 1, 2014
Conversion of convertible notes, shares issued upon conversion	7,981,422
Percentage of shares of common stock issued under the terms of the warrant transactions	19.99%
Convertible Notes conversion rate										$ 16.3084
Conversion price, per share	$ 74.65									$ 61.32
Convertible debt, fair value	316,300,000
Convertible notes, carrying value, net of tax	53,300,000
Convertible notes, fair carrying value	400,000,000
Initial equity component	83,700,000
Proceeds from long-term borrowings	515,000,000	490,000,000	10,018,000
Debt discount	83,700,000
Remaining life of the convertible notes	5.6
Effective interest rate	7.814%
Notional amount	350,000,000
Interest rate swap liability position	14,800,000
Accrued interest	3,100,000
Convertible note hedge transactions, purchased call options	88,000,000
Convertible note hedge transactions, net of tax	56,000,000
Strike price of warrants	$ 74.65
Proceeds from sale of warrants		$ 59,400,000