Financial Instruments (Securities Repurchase and Reverse Repurchase Arrangements) (Details) $ in Millions	3 Months Ended
Mar. 31, 2017 USD ($)
Derivative Instrument Detail [Abstract]
Reverse Repurchase Agreements Maturities	90 days
Securities for Reverse Repurchase Agreements	$ 2,950

The carrying value of securities purchased to be resold in reverse repurchase transactions as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(2)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Name:	us-gaap_SecuritiesForReverseRepurchaseAgreements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant