Recent Accounting Pronouncements Stock Compensation ASU 2016-09 (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Stock Compensation [Abstract]
Net Excess Tax Benefits Recognized in Income Tax Provision	$ 70
Excess Tax Benefit from Share-based Compensation, Operating Activities	$ 70

Amount of cash outflow for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 20
-Section 55
-Paragraph 24
-URI http://asc.fasb.org/extlink&oid=118258462&loc=d3e11374-113907

Name:	us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration