Business Segment Information - Amounts Of Consolidated Revenue, Expense, Tax And Assets (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)
Segment Reporting, Measurement Disclosures [Abstract]
Number of operating segments | segment	4
Segment Reporting Information [Line Items]
Net interest income	$ 294,508	$ 301,173
Provision/(provision credit) for loan losses	9,000	(1,000)
Noninterest income	141,045	136,017
Noninterest expense	296,090	313,265
Income/(loss) before income taxes	130,463	124,925
Provision/(benefit) for income taxes	27,058	29,931
Net income/(loss)	103,405	94,994
Average assets	40,883,192	40,350,724
Regional Banking
Segment Reporting Information [Line Items]
Net interest income	287,157	293,194
Provision/(provision credit) for loan losses	13,958	4,458
Noninterest income	72,117	79,963
Noninterest expense	199,959	201,749
Income/(loss) before income taxes	145,357	166,950
Provision/(benefit) for income taxes	33,693	39,340
Net income/(loss)	111,664	127,610
Average assets	28,889,492	28,171,416
Fixed Income
Segment Reporting Information [Line Items]
Net interest income	7,322	8,475
Noninterest income	53,807	45,605
Noninterest expense	51,227	49,931
Income/(loss) before income taxes	9,902	4,149
Provision/(benefit) for income taxes	2,283	896
Net income/(loss)	7,619	3,253
Average assets	2,849,939	3,479,425
Corporate
Segment Reporting Information [Line Items]
Net interest income	(7,853)	(16,184)
Noninterest income	13,352	9,316
Noninterest expense	40,351	53,329
Income/(loss) before income taxes	(34,852)	(60,197)
Provision/(benefit) for income taxes	(11,403)	(13,771)
Net income/(loss)	(23,449)	(46,426)
Average assets	8,050,162	7,115,661
Non-Strategic
Segment Reporting Information [Line Items]
Net interest income	7,882	15,688
Provision/(provision credit) for loan losses	(4,958)	(5,458)
Noninterest income	1,769	1,133
Noninterest expense	4,553	8,256
Income/(loss) before income taxes	10,056	14,023
Provision/(benefit) for income taxes	2,485	3,466
Net income/(loss)	7,571	10,557
Average assets	$ 1,093,599	$ 1,584,222