Business Segment Information - Amounts Of Consolidated Revenue, Expense, Tax And Assets (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) segment	Mar. 31, 2019 USD ($)
Segment Reporting, Measurement Disclosures [Abstract]
Number of operating segments | segment	4
Segment Reporting Information [Line Items]
Net interest income	$ 302,802	$ 294,508
Provision/(provision credit) for loan losses	145,000	9,000
Noninterest income	174,756	141,045
Noninterest expense	311,319	296,090
Income/(loss) before income taxes	21,239	130,463
Provision/(benefit) for income taxes	4,767	27,058
Net income/(loss)	16,472	103,405
Average assets	43,551,912	40,883,192
Regional Banking
Segment Reporting Information [Line Items]
Net interest income	300,128	286,023
Provision/(provision credit) for loan losses	145,435	13,442
Noninterest income	81,871	73,029
Noninterest expense	211,013	198,569
Income/(loss) before income taxes	25,551	147,041
Provision/(benefit) for income taxes	4,388	34,109
Net income/(loss)	21,163	112,932
Average assets	32,164,347	28,801,849
Fixed Income
Segment Reporting Information [Line Items]
Net interest income	10,914	7,332
Noninterest income	95,723	53,807
Noninterest expense	81,063	50,533
Income/(loss) before income taxes	25,574	10,606
Provision/(benefit) for income taxes	6,099	2,457
Net income/(loss)	19,475	8,149
Average assets	3,764,192	2,848,249
Corporate
Segment Reporting Information [Line Items]
Net interest income	(13,359)	(7,914)
Noninterest income	(3,718)	13,353
Noninterest expense	15,449	41,779
Income/(loss) before income taxes	(32,526)	(36,340)
Provision/(benefit) for income taxes	(6,372)	(11,771)
Net income/(loss)	(26,154)	(24,569)
Average assets	6,784,190	8,058,041
Non-Strategic
Segment Reporting Information [Line Items]
Net interest income	5,119	9,067
Provision/(provision credit) for loan losses	(435)	(4,442)
Noninterest income	880	856
Noninterest expense	3,794	5,209
Income/(loss) before income taxes	2,640	9,156
Provision/(benefit) for income taxes	652	2,263
Net income/(loss)	1,988	6,893
Average assets	$ 839,183	$ 1,175,053