Debt Obligations (5.5% Convertible Senior Notes Narrative) (Details) (Convertible Senior Notes, 5.5% Fixed Rate, Due 2016 [Member], USD $)	1 Months Ended	9 Months Ended
	Jul. 31, 2011	Sep. 30, 2013	Dec. 31, 2012
Convertible Senior Notes, 5.5% Fixed Rate, Due 2016 [Member]
Debt Instrument [Line Items]
Debt aggregate principal amount	$ 135,000,000
Interest rate		5.50%	5.50%
Debt maturity date		Jul. 15, 2016
Conversion rate	54.019
Conversion price per share	$ 18.51
Principal amount of notes	$ 1,000