Notes Payable and Amounts Due Under Repurchase Agreements (2029 Notes Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2009
Debt Instrument [Line Items]
Change in fair value of embedded derivatives	$ (464,698)	$ 32,321	$ 133,968
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
2029 Notes Embedded Conversion Derivative [Member]
Debt Instrument [Line Items]
Change in fair value of embedded derivatives	0	3,809	0
Mandatory Redemption [Member] | 2029 Notes Embedded Conversion Derivative [Member]
Debt Instrument [Line Items]
Change in fair value of embedded derivatives		3,800
December 2029 Notes [Member]
Debt Instrument [Line Items]
Principal amount of convertible senior notes payable at issuance				$ 115,800
Adjustments to additional paid in capital, equity component of convertible debt	15,600
Deferred income tax liability, equity component of convertible debt	$ 11,000
Interest rate	5.25%
Extinguishment of debt, amount			47,500
Extinguishment of debt, cash paid			74,800
Extinguishment of debt, cash paid for shares of common stock			$ 34,900
Extinguishment of debt, shares issued			1,629,677
Extinguishment of debt, carrying value at extinguishment			$ 44,500
Extinguishment of debt, gain (loss), net of tax			$ (5,200)
Interest rate, effective percentage	11.90%
December 2029 Notes [Member] | Private Exchange Offers [Member]
Debt Instrument [Line Items]
Extinguishment of debt, amount		36,200
Extinguishment of debt, cash paid		66,700
Extinguishment of debt, cash paid for shares of common stock		$ 23,200
Extinguishment of debt, shares issued		946,793
Extinguishment of debt, carrying value at extinguishment		$ 34,600
Extinguishment of debt, gain (loss), net of tax		(2,500)
December 2029 Notes [Member] | Mandatory Redemption [Member]
Debt Instrument [Line Items]
Extinguishment of debt, amount		32,100
Extinguishment of debt, cash paid		69,400
Extinguishment of debt, cash paid for shares of common stock		$ 24,600
Extinguishment of debt, shares issued		897,548
Equity reclassified to an embedded derivative liability		$ 58,100