Segment Reporting (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment		3
Segment Income Statement Data Abstract
Net interest income		$ 215,547	$ 209,871
Net intersegment interest income (expense)		0	0
Segment net interest income		215,547	209,871
Noninterest income		91,202	90,380
Total revenue		306,749	300,251
Credit provision		6,000	0
Noninterest Expense		191,671	212,965
Income (loss) before income taxes		109,078	87,285
Income tax expense (benefit)		22,392	17,829
Net income		86,686	69,456
Segment Balance Sheet Data
Allocated Goodwill - Segment		1,168,944	1,153,156
Operating Segments | Corporate and Commercial Specialty
Segment Income Statement Data Abstract
Net interest income		115,909	104,435
Net intersegment interest income (expense)		(22,622)	(8,477)
Segment net interest income		93,287	95,958
Noninterest income		11,445	12,683
Total revenue		104,733	108,641
Credit provision		13,485	10,598
Noninterest Expense		38,788	39,250
Income (loss) before income taxes		52,460	58,793
Income tax expense (benefit)		10,003	11,426
Net income		42,457	47,367
Segment Balance Sheet Data
Allocated Goodwill - Segment		524,525	519,779
Operating Segments | Community, Consumer, and Business
Segment Income Statement Data Abstract
Net interest income		88,072	86,395
Net intersegment interest income (expense)		23,442	17,148
Segment net interest income		111,514	103,543
Noninterest income		74,223	74,036
Total revenue		185,737	177,579
Credit provision		5,033	4,966
Noninterest Expense		130,863	127,144
Income (loss) before income taxes		49,841	45,469
Income tax expense (benefit)		10,443	9,549
Net income		39,398	35,920
Segment Balance Sheet Data
Allocated Goodwill - Segment		644,419	633,377
Operating Segments | Risk Management and Shared Services
Segment Income Statement Data Abstract
Net interest income		11,567	19,041
Net intersegment interest income (expense)		(821)	(8,671)
Segment net interest income		10,746	10,370
Noninterest income		5,533	3,661
Total revenue		16,280	14,031
Credit provision		(12,518)	(15,563)
Noninterest Expense		21,893	46,571
Income (loss) before income taxes		6,905	(16,977)
Income tax expense (benefit)		1,947	(3,146)
Net income		4,958	(13,831)
Segment Balance Sheet Data
Allocated Goodwill - Segment		0	0
Business Combination, Acquisition Related Costs	[1]	$ 632	$ 20,605

[1] Includes Huntington branch and Bank Mutual acquisition related costs only.