Notes Payable and Amounts Due Under Repurchase Agreements (2015 Notes, 2015 Notes Hedges and 2015 Warrants Narrative) (Details) - USD ($) $ in Thousands		12 Months Ended
	Sep. 15, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2010
Debt Instrument [Line Items]
Interest expense on convertible notes		$ 28,849	$ 36,370	$ 38,870
Convertible Debt [Member]
Debt Instrument [Line Items]
Interest expense on convertible notes		1,400	9,000	26,400
2015 Notes Embedded Conversion Derivative [Member]
Debt Instrument [Line Items]
Derivative, liability, fair value at issuance					$ 37,000
Derivative liability, cash paid to settle conversion premium	$ 25,800
September 2015 Notes [Member]
Debt Instrument [Line Items]
Principal amount of convertible senior notes payable at issuance					$ 200,000
Interest rate					3.50%
Deferred financing costs		$ 6,800
Extinguishment of debt, cash paid	48,200			116,100
Extinguishment of debt, amount	$ 22,400			108,000
Extinguishment of debt, cash paid for shares of common stock				$ 79,200
Extinguishment of debt, shares issued				3,643,402
Extinguishment of debt, carrying value at extinguishment				$ 99,600
Extinguishment of debt, gain (loss), net of tax				$ (15,200)
Interest rate, effective percentage		8.90%
September 2015 Notes [Member] | Private Exchange Offers [Member]
Debt Instrument [Line Items]
Extinguishment of debt, cash paid			82,900
Extinguishment of debt, amount			69,600
Extinguishment of debt, cash paid for shares of common stock			$ 48,200
Extinguishment of debt, shares issued			2,115,055
Extinguishment of debt, carrying value at extinguishment			$ 66,000
Extinguishment of debt, gain (loss), net of tax			$ (4,800)