Stockholders' Equity Treasury shares (Details) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation	210,657	223,125	269,865
Equity, Class of Treasury Stock [Line Items]
Treasury Stock Acquired, Average Cost Per Share	$ 45.80	$ 57.88	$ 51.16

Total cost of shares repurchased divided by the total number of shares repurchased.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration