Stock Compensation Plans (Summary of Total Share-Based Compensation Expense and Related Net Tax Benefits) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Total Stock Compensation Expense and Related Net Tax Benefit [Abstract]
Stock compensation costs	$ 8,081	$ 7,057	$ 15,525	$ 13,215
Related net tax benefits for stock compensation plans	$ 1	$ 97	$ 4,708	$ 4,875

Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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Balance Type:	credit
Period Type:	duration