Summary of Accounting Policies - Advertising and Promotion Expenses (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Advertising and promotion expenses	$ 57us-gaap_MarketingAndAdvertisingExpense	$ 53us-gaap_MarketingAndAdvertisingExpense	$ 54us-gaap_MarketingAndAdvertisingExpense

The total expense recognized in the period for promotion, public relations, and brand or product advertising.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.4)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Name:	us-gaap_MarketingAndAdvertisingExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration