Off-Balance Sheet Guarantees and Long Term Standby Purchase Commitments Guarantee and Commitment Obligations Contingency Activity (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Guarantor Obligations [Line Items]
Guaranty Liabilities	$ 37,803	$ 27,440	$ 30,308	$ 48,526
Additions to guarantee and commitment obligations	15,134	5,097	4,539
Adjustments related to new consolidation guidance	0	0	(12,812)
Amortization of the Guarantee and Commitment Obligation	$ 4,771	$ 7,965	$ 9,945