Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Interest Income (Expense), Net	$ 86,321	$ 83,840	$ 81,186	$ 76,283	$ 77,009	$ 77,101	$ 75,851	$ 67,776	$ 327,630	$ 297,737	$ 266,898
Provision for loan losses	(19,159)	13,836	12,224	5,153	(213)	1,967	1,919	2,498	12,054	6,171	7,945
Other Income (Loss) and Security Gains									125,664	97,193	101,101
Noninterest Expense									286,595	263,988	228,755
Income before income taxes	55,475	36,703	35,127	27,340	30,215	37,532	26,548	30,476	154,645	124,771	131,299
Income taxes									26,722	22,071	20,912
Net Income (Loss) Attributable to Parent	45,200	$ 30,846	$ 29,505	$ 22,372	23,936	$ 31,146	$ 22,163	$ 25,455	127,923	102,700	110,387
Assets	9,279,021				8,558,377				9,279,021	8,558,377	7,804,308
Total loans	7,177,785				6,501,404				7,177,785	6,501,404	5,692,132
Total deposits	7,572,358				7,052,612				7,572,358	7,052,612	6,260,860
Depreciation, Amortization and Accretion, Net									10,814	9,112	8,585
Other Noninterest Expense									275,781	254,876	220,170
Totals For Reportable Segments [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net									330,160	298,143	263,595
Income taxes									27,428	26,322	23,785
Assets	9,249,346				8,549,130				9,249,346	8,549,130	7,785,236
Total deposits	7,823,256				7,129,030				7,823,256	7,129,030	6,338,938
Depreciation, Amortization and Accretion, Net									10,814	9,112	8,585
Other Noninterest Expense									260,526	231,799	201,503
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net									1,250	1,250	1,275
Income taxes									0	0	0
Assets	(1,458)				(19,231)				(1,458)	(19,231)	(13,482)
Total deposits	(250,898)				(76,418)				(250,898)	(76,418)	(78,078)
Depreciation, Amortization and Accretion, Net									0	0	0
Other Noninterest Expense									0	0	0
Parent Co Gfsc Totals Not Eliminated [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net									(3,780)	(1,656)	2,028
Income taxes									(706)	(4,251)	(2,873)
Assets	31,133				28,478				31,133	28,478	32,554
Total deposits	0				0				0	0	0
Depreciation, Amortization and Accretion, Net									0	0	0
Other Noninterest Expense									15,255	23,077	18,667
Pnb Segment [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net									326,375	293,130	258,547
Provision for loan losses									30,813	8,356	7,569
Other Income (Loss) and Security Gains									124,231	92,392	88,981
Noninterest Expense									268,938	237,433	206,843
Income before income taxes									150,855	139,733	133,116
Income taxes									27,125	26,133	23,644
Net Income (Loss) Attributable to Parent									123,730	113,600	109,472
Assets	9,236,915				8,521,537				9,236,915	8,521,537	7,753,848
Total loans	7,165,840				6,481,644				7,165,840	6,481,644	5,671,173
Total deposits	7,820,983				7,125,111				7,820,983	7,125,111	6,334,796
GFSC [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net									3,785	5,013	5,048
Provision for loan losses									196	754	1,328
Other Income (Loss) and Security Gains									255	170	187
Noninterest Expense									2,402	3,478	3,245
Income before income taxes									1,442	951	662
Income taxes									303	189	141
Net Income (Loss) Attributable to Parent									1,139	762	521
Assets	12,431				27,593				12,431	27,593	31,388
Total loans	12,757				28,143				12,757	28,143	32,664
Total deposits	2,273				3,919				2,273	3,919	4,142
Other Segments [Member]
Segment Reporting Information [Line Items]
Interest Income (Expense), Net									(2,530)	(406)	3,303
Provision for loan losses									(18,955)	(2,939)	(952)
Other Income (Loss) and Security Gains									1,178	4,631	11,933
Noninterest Expense									15,255	23,077	18,667
Income before income taxes									2,348	(15,913)	(2,479)
Income taxes									(706)	(4,251)	(2,873)
Net Income (Loss) Attributable to Parent									3,054	(11,662)	394
Assets	29,675				9,247				29,675	9,247	19,072
Total loans	(812)				(8,383)				(812)	(8,383)	(11,705)
Total deposits	$ (250,898)				$ (76,418)				$ (250,898)	$ (76,418)	$ (78,078)