Acquisition of Businesses (Details) (USD $)			3 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Ally Financial International Operations [Member]	Dec. 31, 2013 Ally Financial International Operations [Member]	Dec. 31, 2013 Ally FInancial [Member]	Dec. 31, 2013 Scenario, Forecast [Member] Gmac Saic [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred				$ 3,300,000,000
Business Combination, Consideration Transferred, Liabilities Incurred			1,400,000,000
Business Combination, Contingent Consideration, Liability						900,000,000
Goodwill	$ 1,240,000,000	$ 1,108,000,000	$ 132,000,000	$ 132,000,000	$ 132,000,000