[Line Items] for Schedule of Shareholders' Equity [Table]

No definition available.

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
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- Definition

Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.

+ References

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-Publisher FASB
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-SubTopic 10
-Section 45
-Paragraph 15
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- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

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- Definition

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

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- Definition

Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
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- Definition

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

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-Topic 505
-SubTopic 30
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- Definition

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

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- Definition

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

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Shareholders' Equity (Details)								12 Months Ended			103 Months Ended	146 Months Ended	162 Months Ended
Shareholders' Equity (Details)	Nov. 08, 2018 $ / shares	May 18, 2018 $ / shares	Nov. 07, 2017 $ / shares	May 16, 2017 $ / shares	Nov. 09, 2016 $ / shares	May 24, 2016 USD ($) $ / shares	Jul. 16, 2014	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	May 15, 2018 USD ($)	Jun. 02, 2016 USD ($) shares	May 19, 2015 shares
Schedule of Shareholders' Equity [Line Items]
Stock repurchased during period (in shares) \| shares								783,776	522,134	736,171			13,096,804
Aggregate price of shares repurchased since inception \| $								$ 27,942,765	$ 18,234,163	$ 20,139,954			$ 188,521,718
Average price of shares repurchased since inception (per share) \| $ / shares								$ 35.65	$ 34.92	$ 27.36			$ 14.39
Dividends declared (per share) \| $ / shares								$ 0.32	$ 0.26	$ 0.24
Stock split, conversion ratio							1.5
Cash dividends paid \| $								$ 16,700,000	$ 13,700,000	$ 12,700,000
Regular Semi-Annual Dividend
Schedule of Shareholders' Equity [Line Items]
Dividends declared (per share) \| $ / shares	$ 0.16	$ 0.16	$ 0.13	$ 0.13	$ 0.13	$ 0.11
Open market
Schedule of Shareholders' Equity [Line Items]
Stock repurchase program amount authorized (in shares) \| shares															2,000,000.0	5,700,000.0
Stock repurchase program amount authorized, value \| $						$ 25,000,000								$ 15,000,000.0	$ 25,000,000
Stock repurchased during period (in shares) \| shares								252,272	8,676	165,598	4,095,767
Aggregate price of shares repurchased since inception \| $								$ 8,373,698	$ 283,654	$ 4,440,658	$ 69,605,813
Average price of shares repurchased since inception (per share) \| $ / shares								$ 33.19	$ 32.69	$ 26.82	$ 16.99
401(k)
Schedule of Shareholders' Equity [Line Items]
Stock repurchased during period (in shares) \| shares								497,753	467,580	540,501			7,047,776
Aggregate price of shares repurchased since inception \| $								$ 18,472,442	$ 16,336,084	$ 14,875,850			$ 100,541,247
Average price of shares repurchased since inception (per share) \| $ / shares								$ 37.11	$ 34.94	$ 27.52			$ 14.27
Directors & employees
Schedule of Shareholders' Equity [Line Items]
Stock repurchased during period (in shares) \| shares								33,751	45,878	30,072		1,953,261
Aggregate price of shares repurchased since inception \| $								$ 1,096,625	$ 1,614,425	$ 823,446		$ 18,374,658
Average price of shares repurchased since inception (per share) \| $ / shares								$ 32.49	$ 35.19	$ 27.38		$ 9.41