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Restricted Stock Units Issued (Detail) - Restricted Stock Units (RSUs) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Restricted Stock Units
Beginning Restricted Stock Units	52,224	43,345
Restricted Stock Units Granted	7,892	7,522
Dividend Equivalents Earned	1,673	1,357
Restricted Stock Units Settled	0	0
Ending Restricted Stock Units	61,789	52,224
Weighted-Average Stock Price
Beginning Restricted Stock Units	$ 36.22	$ 33.40
Restricted Stock Units Granted	49.63	50.23
Dividend Equivalents Earned	47.85	48.57
Restricted Stock Units Settled	0	0
Ending Restricted Stock Units	$ 38.25	$ 36.22

X

- Definition

The number of grants made 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

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- Definition

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- Definition

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