Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
INTEREST INCOME
Interest and fees on loans and leases	$ 951,439	$ 1,051,077	$ 972,114
Interest and dividends on investment securities:
Taxable	47,739	56,150	76,014
Exempt from federal income tax	6,095	7,400	8,368
Dividends	2,615	2,269	1,988
Interest on temporary investments and interest bearing deposits	4,739	14,180	8,665
Total interest income	1,012,627	1,131,076	1,067,149
INTEREST EXPENSE
Interest on deposits	100,200	167,941	92,685
Interest on securities sold under agreement to repurchase and federal funds purchased	766	2,092	506
Interest on borrowings	13,921	17,564	13,604
Interest on junior subordinated debentures	15,221	22,845	21,715
Total interest expense	130,108	210,442	128,510
Net interest income	882,519	920,634	938,639
Provision for credit losses	204,861	72,515	55,905
Net interest income after provision for credit losses	677,658	848,119	882,734
NON-INTEREST INCOME
Residential mortgage banking revenue, net	270,822	101,810	118,235
Gain (loss) on sale of debt securities, net	190	(7,184)	14
Gain (loss) on equity securities, net	769	83,475	(1,484)
Gain on loan and lease sales, net	6,707	10,467	7,834
BOLI income	8,399	8,406	8,297
Total non-interest income	412,009	339,824	279,417
NON-INTEREST EXPENSE
Salaries and employee benefits	479,247	420,373	425,575
Occupancy and equipment, net	151,650	144,236	148,724
Communications	11,843	14,583	17,233
Marketing	8,313	13,255	11,313
Services	46,640	54,111	62,730
FDIC assessments	12,516	11,233	16,094
Intangible amortization	4,986	5,618	6,166
Goodwill impairment	1,784,936	0	0
Other expenses	45,956	55,631	51,630
Total non-interest expense	2,546,087	719,040	739,465
(Loss) income before income taxes	(1,456,420)	468,903	422,686
(Benefit) provision for income taxes	67,000	114,808	106,423
Net Income (Loss) Attributable to Parent, Total	$ (1,523,420)	$ 354,095	$ 316,263
Earnings Per Share [Abstract]
Basic earnings per common share (usd per share)	$ (6.92)	$ 1.61	$ 1.44
Diluted earnings per common share (usd per share)	$ (6.92)	$ 1.60	$ 1.43
Weighted average number of common shares outstanding:
Basic (in shares)	220,218	220,339	220,280
Diluted (in shares)	220,218	220,650	220,737
Service charges on deposits
NON-INTEREST INCOME
Revenue from Contract with Customer	$ 58,561	$ 64,514	$ 62,124
Brokerage revenue
NON-INTEREST INCOME
Revenue from Contract with Customer	15,599	15,877	16,480
Other income
NON-INTEREST INCOME
Revenue from Contract with Customer	$ 50,962	$ 62,459	$ 67,917