Convertible Notes Schedule of Maturities of Long-term Debt (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 177,387
Long-term Debt, Maturities, Repayments of Principal in Year Two	300,000
Long-term Debt	477,387
Series 2012 Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	22,337
Long-term Debt, Maturities, Repayments of Principal in Year Two	0
Long-term Debt	22,337
May 2015 Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	155,050
Long-term Debt, Maturities, Repayments of Principal in Year Two	0
Long-term Debt	155,050
Term Loan. [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	0
Long-term Debt, Maturities, Repayments of Principal in Year Two	300,000
Long-term Debt	$ 300,000