Notes Payable - Convertible (Details) (USD $)	3 Months Ended		1 Months Ended	3 Months Ended			0 Months Ended	3 Months Ended			12 Months Ended		3 Months Ended	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Jan. 31, 2013 2026 Notes	Mar. 31, 2014 2026 Notes	Mar. 31, 2013 2026 Notes	Dec. 31, 2012 2026 Notes	Jul. 11, 2013 2028 Notes	Mar. 31, 2014 2028 Notes	Sep. 30, 2013 2028 Notes	Mar. 31, 2013 2028 Notes	Dec. 31, 2013 2028 Notes	Dec. 31, 2012 2028 Notes	Mar. 31, 2013 Convertible Debt	Dec. 31, 2013 Common Stock
Debt Instrument [Line Items]
Stated interest rate				3.95%				5.125%
Noncash interest charges													$ 2,858,000
Contractual interest expense	302,000	1,356,000											1,122,000
Amortization of debt costs													305,000
Total interest expense			137,000	0	0			0		0	195,000		4,285,000
Outstanding principal balance						15,537,000						223,035,000
Repayments of convertible debt	0	20,565,000	20,702,000								226,427,000
Settled			15,537,000				130,000		222,905,000		223,035,000
Decrease to APIC, conversion of debt			$ 5,028,000								$ 3,197,000
Conversion period based on average daily closing price											20 days
Shares of common stock														2,407,911