Notes Payable - Convertible (Details) (USD $)	3 Months Ended	9 Months Ended		1 Months Ended	3 Months Ended		9 Months Ended			0 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Jan. 31, 2013 2026 Notes	Sep. 30, 2014 2026 Notes	Sep. 30, 2013 2026 Notes	Sep. 30, 2014 2026 Notes	Sep. 30, 2013 2026 Notes	Dec. 31, 2012 2026 Notes	Jul. 11, 2013 2028 Notes	Sep. 30, 2014 2028 Notes	Sep. 30, 2013 2028 Notes	Sep. 30, 2014 2028 Notes	Dec. 31, 2013 2028 Notes	Dec. 31, 2012 2028 Notes	Sep. 30, 2013 Convertible Debt 2028 Notes	Sep. 30, 2013 Convertible Debt 2028 Notes	Dec. 31, 2013 Common Stock
Debt Instrument [Line Items]
Outstanding principal balance									$ 15,537,000						$ 223,035,000
Stated interest rate					3.95%		3.95%				5.125%		5.125%
Repayments of convertible debt		0	246,797,000	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
Noncash interest charges																26,000	5,400,000
Contractual interest expense		924,000	2,888,000													0	2,072,000
Amortization of debt costs																0	566,000
Total interest expense	$ 26,000		$ 8,038,000	$ 137,000	$ 0	$ 0	$ 0	$ 0			$ 0		$ 0	$ 195,000