Stock-Based Compensation Market Stock Units (Details)	3 Months Ended
Mar. 31, 2018 shares
Maximum [Member]
Stock-Based Compensation Details
Equity Share Payout Range	48,291
MSU [Member]
Stock-Based Compensation Details
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	32,194

Net number of non-option equity instruments granted to participants.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration