Segment Reporting (Details) - USD ($)		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Segment Income Statement Data Abstract
Net interest income		$ 202,942,000	$ 215,547,000
Net intersegment interest income (expense)		0	0
Segment net interest income		202,942,000	215,547,000
Noninterest income		98,306,000	91,202,000
Total revenue		301,248,000	306,749,000
Credit provision		53,001,000	6,000,000
Noninterest expense		192,191,000	191,671,000
Income (loss) before income taxes		56,056,000	109,078,000
Income tax expense (benefit)		10,219,000	22,392,000
Net income		45,838,000	86,686,000
Segment Balance Sheet Data
Allocated goodwill		1,191,388,000	1,168,944,000
Operating Segments | Corporate and Commercial Specialty
Segment Income Statement Data Abstract
Net interest income		113,478,000	124,294,000
Net intersegment interest income (expense)		(12,336,000)	(19,927,000)
Segment net interest income		101,141,000	104,368,000
Noninterest income		34,802,000	27,394,000
Total revenue		135,943,000	131,762,000
Credit provision		13,174,000	13,833,000
Noninterest expense		52,598,000	56,340,000
Income (loss) before income taxes		70,172,000	61,589,000
Income tax expense (benefit)		13,126,000	11,920,000
Net income		57,046,000	49,669,000
Segment Balance Sheet Data
Allocated goodwill		530,144,000	528,832,000
Operating Segments | Community, Consumer, and Business
Segment Income Statement Data Abstract
Net interest income		74,927,000	79,686,000
Net intersegment interest income (expense)		18,685,000	20,747,000
Segment net interest income		93,612,000	100,433,000
Noninterest income		57,650,000	58,275,000
Total revenue		151,262,000	158,708,000
Credit provision		5,108,000	4,685,000
Noninterest expense		116,431,000	112,917,000
Income (loss) before income taxes		29,723,000	41,106,000
Income tax expense (benefit)		6,242,000	8,632,000
Net income		23,481,000	32,473,000
Segment Balance Sheet Data
Allocated goodwill		661,244,000	640,112,000
Operating Segments | Risk Management and Shared Services
Segment Income Statement Data Abstract
Net interest income		14,537,000	11,567,000
Net intersegment interest income (expense)		(6,349,000)	(821,000)
Segment net interest income		8,188,000	10,746,000
Noninterest income		5,854,000	5,533,000
Total revenue		14,042,000	16,280,000
Credit provision		34,719,000	(12,518,000)
Noninterest expense		23,162,000	22,414,000
Income (loss) before income taxes		(43,838,000)	6,384,000
Income tax expense (benefit)		(9,149,000)	1,840,000
Net income		(34,689,000)	4,543,000
Segment Balance Sheet Data
Allocated goodwill		0	0
Business Combination, Acquisition Related Costs	[1]	$ 1,721,000	$ 632,000

[1] (b) Includes Huntington branch and First Staunton acquisition related costs only.