Guarantees and Indemnifications Guarantees (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 2018 Senior Notes [Member]	Dec. 31, 2013 2018 Senior Notes [Member]	Mar. 31, 2014 2017 Convertible Senior Notes [Member]	Dec. 31, 2013 2017 Convertible Senior Notes [Member]	Mar. 31, 2014 2018 Convertible Senior Notes [Member]	Dec. 31, 2013 2018 Convertible Senior Notes [Member]	Mar. 31, 2014 Face Value [Member] 2018 Senior Notes [Member]	May 08, 2012 Face Value [Member] 2018 Senior Notes [Member]	Nov. 12, 2010 Face Value [Member] 2018 Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes			$ 228,169,000	$ 228,070,000					$ 230,000,000	$ 30,000,000	$ 200,000,000
Debt Instrument, Interest Rate, Stated Percentage			8.625%		3.25%		3.00%
Convertible senior subordinated notes					57,500,000	57,500,000	86,250,000	86,250,000
Total of Loans Covered by Guarantees	6,500,000	5,200,000
Total of Guaranteed Loans Inquired About	7,900,000	8,200,000
Total Loans Indemnified to third parties	1,600,000	1,500,000
Loan Repurchase Guarantee Liability	$ 2,800,000	$ 3,100,000