Guarantees and Long Term Standby Purchase Commitments - Schedule of Guarantee and Commitment Obligations (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Loss Contingencies [Line Items]
Guarantee and commitment obligation		$ 37,282	$ 38,609	$ 37,925	$ 39,667
Term of Guarantees Minimum		1 year
Term of Guarantees Maximum		30 years
Additions to guarantee and commitment obligations	[1]	$ 6,725	8,207	4,966
Amortization of the Guarantee and Commitment Obligation		(8,052)	(7,523)	$ (6,708)
Guarantee obligations issued after January 1, 2003 [Member]
Loss Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		4,900,000	4,500,000
Guarantee obligations issued prior to January 1, 2003 [Member]
Loss Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		$ 40,100	$ 56,200

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