Derivative Financial Instruments and Risk Management (Details 3) (USD $) In Billions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative
Derivative instruments, notional amount	$ 5.25invest_DerivativeNotionalAmount	$ 6.74invest_DerivativeNotionalAmount	$ 9.82invest_DerivativeNotionalAmount

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