Fair Value and Investment Securities Distribution of Financial Instruments, Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		$ 875	$ 1,199
Fair Value, Inputs, Level 1
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis	[1]	33	98
Fair Value, Inputs, Level 2
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		842	1,101
Fair Value, Inputs, Level 3
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		0	0
Municipal securities
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		62	135
Municipal securities | Fair Value, Inputs, Level 1
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis	[1]	0	0
Municipal securities | Fair Value, Inputs, Level 2
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		62	135
Municipal securities | Fair Value, Inputs, Level 3
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		0	0
U.S. government and agency securities
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis	[2]	72	199
U.S. government and agency securities | Fair Value, Inputs, Level 1
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis	[1],[2]	31	85
U.S. government and agency securities | Fair Value, Inputs, Level 2
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis	[2]	41	114
U.S. government and agency securities | Fair Value, Inputs, Level 3
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis	[2]	0	0
Corporate securities
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		630	618
Corporate securities | Fair Value, Inputs, Level 1
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis	[1]	0	0
Corporate securities | Fair Value, Inputs, Level 2
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		630	618
Corporate securities | Fair Value, Inputs, Level 3
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		0	0
Asset-backed securities
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		57	178
Asset-backed securities | Fair Value, Inputs, Level 1
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis	[1]	0	0
Asset-backed securities | Fair Value, Inputs, Level 2
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		57	178
Asset-backed securities | Fair Value, Inputs, Level 3
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		0	0
Other
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		54	69
Other | Fair Value, Inputs, Level 1
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis	[1]	2	13
Other | Fair Value, Inputs, Level 2
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		52	56
Other | Fair Value, Inputs, Level 3
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value, Measured on Recurring Basis		$ 0	$ 0

[1] During 2015, U.S. government securities were reclassified from Level 2 to Level 1 due to a reassessment of the availability of quoted prices. Prior period amounts have been revised to conform to the 2015 presentation.

[2] Excludes amounts held in escrow related to the U.S. merchant class litigation settlement of $541 million and $540 million at December 31, 2015 and December 31, 2014, which would be included in Level 1 of the Valuation Hierarchy. See Note 10 (Accrued Expenses and Accrued Litigation) and Note 18 (Legal and Regulatory Proceedings) for further details.