Debt (Narrative) (Details) (USD $)	0 Months Ended			1 Months Ended			3 Months Ended				12 Months Ended			0 Months Ended	1 Months Ended	3 Months Ended	64 Months Ended
	Sep. 28, 2012	Jun. 17, 2008	Jun. 11, 2008 warrant	Jun. 30, 2013	Aug. 31, 2011	Jun. 30, 2011	Dec. 31, 2013	Jun. 14, 2013	Mar. 31, 2013	Jun. 30, 2011	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 23, 2012	Feb. 28, 2009	Sep. 30, 2011	Dec. 31, 2014	Feb. 06, 2009	Sep. 27, 2012	Jan. 11, 2008
Debt [Line Items]
Maximum Amount of Net Auction Guarantees Permissible											$ 600,000,000						$ 600,000,000
Credit facility borrowings							0				445,000,000	0					445,000,000
York mortgage property maturity date											July 1, 2035
Debt instrument stated interest percentage							3.125%					3.125%
Amortization of debt discount to interest expenses																		22,900,000
Incremental Credit Facility Extension Period											365 days
Percentage of principal amount debt as component of premium price	1.00%
Maximum percentage of redeemable 2022 senior note	35.00%
Redemption price percentage of 2022 Senior Notes	105.25%
Proceeds from issuance of senior notes											0	0	300,000,000
Extinguishment of debt											0	0	15,020,000
Conversion per principal value of convertible notes		1,000
Repayments of Principal Amount of Convertible Debt								181,900,000
Repayments of Convertible Debt											0	197,371,000	0
Liability for Conversion Option Reclassified to Stockholders Equity									21,800,000	8,200,000
Embedded net of tax									12,000,000	5,400,000
Payments for (Proceeds from) Derivative Instrument, Financing Activities			40,600,000	15,500,000	4,400,000						0	(15,503,000)	0
Carrying value of convertible note hedge recorded in equity, net of taxes									12,000,000
Convertible note hedge reclassification						8,200,000
Convertible note hedge reclassification net of taxes						5,300,000
Carrying Value Of Convertible Note Hedge Reclassified to Other Current Assets									21,800,000
Incremental common shares attributable to call options and warrants (shares)			5,900,000								0	49,000	0
Common stock price per share to be acquired through warrant (usd per share)			$ 44.50
Warrant exercise price (usd per share)			$ 44.50
Net proceeds from sale of warrant			22,300,000
Warrant Exercise Daily Limit			118,348
Warrant Exercise Daily Limit Time Period			50 days
Stock Issued During Period, Shares, Other							722,288
Interest paid											42,400,000	33,200,000	34,900,000
Senior Notes [Member]
Debt [Line Items]
Debt instrument stated interest percentage		7.75%
Aggregate principal value of debt		150,000,000
Proceeds from issuance of senior notes		145,900,000
Effective interest rate		8.00%
Long-term Debt, Gross														80,000,000
Early repayment of senior debt														97,000,000
Interest payable, current														2,700,000
Redemption Premium														14,000,000
Extinguishment of debt													15,000,000
Write-off of unamortized discount													1,000,000
Convertible Notes Member
Debt [Line Items]
Aggregate principal value of debt		200,000,000
Debt instrument maturity date											June 15, 2013
Stated interest rate of convertible debt		3.125%
Net proceeds from convertible notes		194,300,000
Convertible notes conversion ratio		29.5920
Convertible notes conversion price (usd per share)		$ 33.79
Convertible notes payable		161,800,000
Estimated debt rate		7.75%
Reclassification to equity		38,200,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt		21,000,000
Repayments of Principal Amount of Convertible Debt						18,100,000
Repayments of Convertible Debt						22,500,000
Interest Expense, Debt											0	6,417,000	13,470,000
Convertible Note Hedge And Warrant Transactions [Member]
Debt [Line Items]
Carrying value of convertible note hedge recorded in equity, net of taxes			22,500,000
York Property Mortgage Member [Member]
Debt [Line Items]
Fair value											222,000,000						222,000,000	212,100,000
2022 Senior Notes
Debt [Line Items]
Debt instrument stated interest percentage																			5.25%
Fair value											283,500,000						283,500,000
Aggregate principal value of debt																			300,000,000
Debt instrument maturity date											October 1, 2022
Net proceeds from issuance of long term debt	293,700,000
Percentage of senior notes principal as part of redemption price	100.00%
Minimum [Member]
Debt [Line Items]
Covenants, aggregate borrowing availability											100,000,000						100,000,000
Covenant, total liquidity amount											200,000,000						200,000,000
Minimum [Member] | York Property Mortgage Member [Member]
Debt [Line Items]
Debt instrument stated interest percentage											5.60%						5.60%
Maximum [Member] | York Property Mortgage Member [Member]
Debt [Line Items]
Debt instrument stated interest percentage											10.60%						10.60%
York Property Mortgage Member
Debt [Line Items]
Unamortized discount							5,346,000				1,782,000	5,346,000					1,782,000
Long-term debt							218,778,000				218,728,000	218,778,000					218,728,000
Convertible Notes Member
Debt [Line Items]
Unamortized discount							3,796,000				0	3,796,000					0
Senior Notes [Member]
Debt [Line Items]
Unamortized discount							0				0	0					0
Long-term debt							300,000,000				300,000,000	300,000,000					300,000,000
Signing Of Related Purchase And Sale Agreement On January 11, 2008 [Member]
Debt [Line Items]
Components of purchase price of land and buildings																				50,000,000
Purchase Consummated On February 6, 2009 [Member]
Debt [Line Items]
Property acquisition price																		370,000,000
Components of purchase price of land and buildings																		85,000,000
Assumption Of Existing Mortgage [Member]
Debt [Line Items]
Components of purchase price of land and buildings																		235,000,000
Fees paid in conjunction with assumption of mortgage property															2,400,000
Revolving Credit Facility [Member]
Debt [Line Items]
Credit facility borrowings							0					0
Convertible Notes Member
Debt [Line Items]
Repayments of Convertible Debt								197,400,000
Debt Instrument, Convertible, Beneficial Conversion Feature						4,400,000		15,500,000
Write off of Deferred Debt Issuance Cost																1,500,000
New Credit Agreement [Member]
Debt [Line Items]
Borrowing base											757,085,000						757,085,000
Credit facility borrowings											445,000,000						445,000,000
Line of credit, remaining borrowing capacity											312,085,000						312,085,000
Increase in borrowing capacity											100,000,000						100,000,000
Line of credit, sub limit											200,000,000						200,000,000
Total facility fees paid											5,400,000						18,500,000
Debt instrument maturity date											August 22, 2019
Maximum borrowing capacity											850,000,000						850,000,000
Finance Segment Credit Agreement [Member]
Debt [Line Items]
Borrowing base											519,255,000						519,255,000
Credit facility borrowings											445,000,000						445,000,000
Line of credit, remaining borrowing capacity											74,255,000						74,255,000
Line of credit, sub limit											150,000,000						150,000,000
Maximum borrowing capacity											550,000,000						550,000,000
Interest paid											11,200,000
Interest Expense, Debt											7,700,000
Amortization of Financing Costs											1,000,000
Line of Credit Facility, Interest Rate During Period											2.90%
Agency Segment Credit Agreement [Member]
Debt [Line Items]
Borrowing base											237,830,000						237,830,000
Credit facility borrowings											0						0
Line of credit, remaining borrowing capacity											237,830,000						237,830,000
Line of credit, sub limit											50,000,000						50,000,000
Maximum borrowing capacity											300,000,000						300,000,000
Interest paid											31,200,000
Incremental Credit Facility [Member]
Debt [Line Items]
Borrowing base											$ 50,000,000						$ 50,000,000
Debt instrument maturity date											August 21, 2015