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Share-Based Payments (Weighted-Average Fair Value of Options and Stock Per Share) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Stock Units (RSUs) [Member]
Stock, weighted average grant date fair value	$ 55.96	$ 42.66	$ 32.53
Employee Stock Purchase Plan [Member]
Options, weighted average grant date fair value	2.67	2.73	2.63
15% of grant date market value	8.50	7.06	5.23
Total ESPP	11.17	9.79	7.86
Agent Stock Purchase Plan [Member]
Stock, weighted average grant date fair value	$ 5.99	$ 5.04	$ 3.79

X

- Definition

The weighted average fair value discount at grant date, for employee stock purchase plan shares issued during the period.

+ References

No definition available.

+ Details

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X

- Definition

The total weighted average fair value at grant date for employee stock purchase plan shares issued during the period.

+ References

No definition available.

+ Details

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X

- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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 (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

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 (d)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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