Securities (Unrecognized Gains And Losses Securities Held To Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	$ 245,692	$ 257,665
Gross Unrecognized Gains	644	1,443
Gross Unrecognized Losses	(8,350)	(3,694)
Amortized Cost	253,398	259,916
State And Municipal Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	132,317	136,490
Gross Unrecognized Gains	529	1,121
Gross Unrecognized Losses	(3,788)	(1,530)
Amortized Cost	135,576	136,899
Mortgage-Backed Securities - Agency/Residential [Member]
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	97,333	103,925
Gross Unrecognized Gains	115	315
Gross Unrecognized Losses	(4,339)	(2,088)
Amortized Cost	101,557	105,698
Asset-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	14,842	16,050
Gross Unrecognized Gains		7
Gross Unrecognized Losses	(223)	(76)
Amortized Cost	15,065	16,119
Other [Member]
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	1,200	1,200
Amortized Cost	$ 1,200	$ 1,200

Guaranty Bancorp 10-Q