Stock-Based Compensation (Narrative) (Details) $ / shares in Units, $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($) $ / shares
Stock-Based Compensation [Abstract]
Weighted-average fair value of options granted \| $ / shares	$ 33.00
Total intrinsic value for options exercised \| $	$ 44.2

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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