Stockholders' Equity Shares Repurchases (Details) - 2018 Stock Repurchase Program [Member] [Member] - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2019	Dec. 01, 2018	Jun. 30, 2018
Equity, Class of Treasury Stock [Line Items]
Accelerated Share Repurchases, Settlement (Payment) or Receipt			$ 30.0
Stock Repurchase Program, Authorized Amount	$ 70.0	$ 100.0
Treasury Stock, Shares, Acquired	505,448
Treasury Stock Acquired, Average Cost Per Share	$ 59.35

Amount of cash receipt from (payment to) bank; or stock received from (issuance to) bank in the settlement of the accelerated share repurchase agreement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 25
-Paragraph 5
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount of stock repurchase plan authorized.

+ References

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- Definition

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

+ References

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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Number of shares that have been repurchased during the period and are being held in treasury.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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