CONSOLIDATED STATEMENTS OF EARNINGS (Unaudited) (Parenthetical)	3 Months Ended
Mar. 31, 2021
Income Statement [Abstract]
Percentage of adjusted effect of stock dividend issued	10.00%

Percentage of adjusted effect of stock dividend issued.

No definition available.

Name:	gnty_PercentageOfAdjustedEffectOfStockDividendIssued
Namespace Prefix:	gnty_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration