Variable Interest Entities ("VIE's") (CLN Structures Summary Information ) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2017 USD ($)
Credit Linked Note Structure December 2006 [Member]
Credit Linked Notes Structures Summary Information [Line Items]
Amount of Issuance	$ 400
Maturity	Dec. 20, 2016
Credit Linked Note Structure April 2007 [Member]
Credit Linked Notes Structures Summary Information [Line Items]
Amount of Issuance	$ 200
Maturity	Mar. 20, 2017