Notes Payable - Convertible (Details) (USD $)	9 Months Ended		1 Months Ended			0 Months Ended	3 Months Ended	9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Jan. 31, 2013 2026 Notes [Member]	Sep. 30, 2013 2026 Notes [Member]	Dec. 31, 2012 2026 Notes [Member]	Jul. 11, 2013 2028 Notes [Member]	Sep. 30, 2013 2028 Notes [Member]	Sep. 30, 2013 2028 Notes [Member]	Dec. 31, 2012 2028 Notes [Member]	Sep. 30, 2013 Convertible Debt [Member]	Sep. 30, 2012 Convertible Debt [Member]	Sep. 30, 2013 Convertible Debt [Member]	Sep. 30, 2012 Convertible Debt [Member]	Sep. 30, 2013 Common Stock [Member]
Debt Instrument [Line Items]
Stated interest rate				3.95%			5.125%	5.125%
Settled			$ 15,537,000			$ 130,000	$ 222,905,000	$ 223,035,000
Outstanding principal balance					15,537,000				223,035,000
Repayments of convertible debt	246,797,000	0	20,702,000					226,427,000
Noncash interest charges										26,000	4,227,000	5,400,000	12,682,000
Contractual interest expense	2,888,000	3,641,000								0	1,082,000	2,072,000	3,189,000
Amortization of debt costs										0	291,000	566,000	851,000
Total interest expense			137,000					195,000		26,000	5,600,000	8,038,000	16,722,000
Conversion period based on average daily closing price								20 days
Decrease to APIC, conversion of debt			$ 5,028,000					$ 3,197,000
Shares of common stock														2,407,911