Supplemental Equity and Comprehensive Income Information (Details 7) (USD $) In Billions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2015	Mar. 31, 2014
Supplemental Equity and Comprehensive Income Information
Dividends that have been declared but not yet paid (in dollars per share)	$ 1.025	$ 0.855
Dividends paid in current period (in dollars per share)			$ 1.025	$ 0.855
Increase of Current Liabilities due to dividend declared but not paid	$ 0.6us-gaap_DividendsPayableCurrent	$ 0.6us-gaap_DividendsPayableCurrent

Carrying value as of the balance sheet date of dividends declared but unpaid on equity securities issued by the entity and outstanding. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Current Liabilities

-URI http://asc.fasb.org/extlink&oid=6509677

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6935-107765

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.20)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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