Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 255,479	$ 242,299	$ 246,680	$ 268,169	$ 282,030	$ 285,187	$ 281,600	$ 282,259	$ 1,012,627	$ 1,131,076	$ 1,067,149
Interest expense	20,572	25,725	34,177	49,634	55,216	56,214	54,438	44,574	130,108	210,442	128,510
Net interest income	234,907	216,574	212,503	218,535	226,814	228,973	227,162	237,685	882,519	920,634	938,639
Provision for credit losses	29	(338)	87,085	118,085					204,861	72,515	55,905
Provision for loan and lease losses					16,252	23,227	19,352	13,684		72,515	55,905
Non-interest income	123,960	131,924	115,480	40,645	83,749	88,512	121,823	45,740	412,009	339,824	279,417
Non-interest expense	211,312	190,207	181,910	1,962,658	183,443	183,590	180,415	171,592	2,546,087	719,040	739,465
(Loss) income before income taxes	147,526	158,629	58,988	(1,821,563)	110,868	110,668	149,218	98,149	(1,456,420)	468,903	422,686
(Benefit) provision for income taxes	(3,204)	33,758	6,062	30,384	27,118	26,166	37,408	24,116	67,000	114,808	106,423
Net Income (Loss) Attributable to Parent	$ 150,730	$ 124,871	$ 52,926	$ (1,851,947)	$ 83,750	$ 84,502	$ 111,810	$ 74,033	$ (1,523,420)	$ 354,095	$ 316,263
Basic earnings per common share (usd per share)	$ 0.68	$ 0.57	$ 0.24	$ (8.41)	$ 0.38	$ 0.38	$ 0.51	$ 0.34	$ (6.92)	$ 1.61	$ 1.44
Diluted earnings per common share (usd per share)	0.68	0.57	0.24	(8.41)	0.38	0.38	0.51	0.34	$ (6.92)	$ 1.60	$ 1.43
Cash dividends declared per common share (usd per share)	$ 0.21	$ 0.21	$ 0	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21