Debt Obligations Debt Obligations (Outstanding Unsecured Notes in Series of Transactions) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	$ 12,986
Extinguishment of Debt, Principal	11,900
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	(1,127)
Write off of Deferred Debt Issuance Cost	23
2014 5.400% Notes
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	6,570
Extinguishment of Debt, Principal	6,180
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	(401)
Write off of Deferred Debt Issuance Cost	7
2015 7.500% Notes
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	5,843
Extinguishment of Debt, Principal	5,210
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	(663)
Write off of Deferred Debt Issuance Cost	15
2016 6.000% Notes
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	573
Extinguishment of Debt, Principal	510
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	(63)
Write off of Deferred Debt Issuance Cost	$ 1