Debt Obligations Debt Obligations (Outstanding Unsecured Notes in Series of Transactions) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	$ 12,871
Extinguishment of Debt, Amount	11,795
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	1,116
Write off of Deferred Debt Issuance Cost	23
Senior notes 5.400 Percent due 2014 [Member]
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	6,570
Extinguishment of Debt, Amount	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
Senior Notes Due2015 [Member]
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	5,728
Extinguishment of Debt, Amount	5,105
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	652
Write off of Deferred Debt Issuance Cost	15
Senior Notes Due2016 [Member]
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	573
Extinguishment of Debt, Amount	510
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	63
Write off of Deferred Debt Issuance Cost	$ 1