Debt Obligations (Outstanding Unsecured Notes in Series of Transactions) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Extinguishment of Debt [Line Items]
Repayments of unsecured notes	$ 120,361	$ 13,027
Extinguishment of Debt, Amount	117,755
2014 5.400% Notes
Extinguishment of Debt [Line Items]
Repayments of unsecured notes	75,531
Extinguishment of Debt, Amount	75,049
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	527
Write off of Deferred Debt Issuance Cost	5
2015 7.500% Notes
Extinguishment of Debt [Line Items]
Repayments of unsecured notes	44,593
Extinguishment of Debt, Amount	42,706
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	2,079
Write off of Deferred Debt Issuance Cost	41
Discharge of Debt [Member]
Extinguishment of Debt [Line Items]
Repayments of unsecured notes	120,124
Extinguishment of Debt, Amount	117,755
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	2,606
Write off of Deferred Debt Issuance Cost	$ 46