Contingencies and Litigation - Other Contingencies (Details) loans in Millions, $ in Millions	Jun. 30, 2016 USD ($) loans
Letter of Credit [Member]
Guarantor Obligations [Line Items]
Maximum exposure, undiscounted	$ 367
Surety Bond [Member]
Guarantor Obligations [Line Items]
Maximum exposure, undiscounted	$ 783
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Guarantor Obligations [Line Items]
Outstanding Student Loan Portfolio, Loans \| loans	1.7
Outstanding Principal Balance - Student Loan Portfolio	$ 25,500
Reserves for losses on defaulted loans	$ 4

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

Name:	us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant