Risk Management Interest Rate Risk Management (Details) - Interest rate swap agreements - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Derivative [Line Items]
Derivative, Notional Amount	$ 9,775	$ 11,000
Fair Value Hedging [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 8,475	$ 9,700

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant