Off-Balance Sheet Guarantees and Long Term Standby Purchase Commitments - Schedule of Guarantor Obligations Activity (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Commitments and Contingencies Disclosure [Abstract]
Guarantee and commitment obligation	$ 37,925		$ 39,667		$ 37,803		$ 27,440
Additions to guarantee and commitment obligations	4,966	[1]	8,414	[1]	15,134	[1]
Amortization of the Guarantee and Commitment Obligation	$ 6,708		$ 6,550		$ 4,771

[1] Represents the fair value of the guarantee and commitment obligation at inception.