Business Segment Information - Amounts Of Consolidated Revenue, Expense, Tax And Assets (Details) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($)
Segment Reporting, Measurement Disclosures [Abstract]
Number of operating segments | segment							4
Segment Reporting Information [Line Items]
Net interest income	$ 300,676			$ 305,700			$ 898,794	$ 917,805
Provision/(provision credit) for loan losses	15,000			2,000			37,000	1,000
Noninterest income	171,735			348,972			470,773	612,514
Noninterest expense	307,672			294,031			904,156	940,064
Income/(loss) before income taxes	149,739			358,641			428,411	589,255
Provision/(benefit) for income taxes	35,796			83,925			97,321	133,553
Net income/(loss)	113,943	$ 113,742	$ 103,405	274,716	$ 85,992	$ 94,994	331,090	455,702
Average assets	41,940,901			40,077,033			41,359,574	40,199,487
Expenses associated with rebranding initiatives	3,100						12,200
Regional Banking
Segment Reporting Information [Line Items]
Net interest income	302,370			301,099			885,622	899,183
Provision/(provision credit) for loan losses	20,472			7,205			51,690	16,155
Noninterest income	85,776			80,705			240,281	241,760
Noninterest expense	193,211			207,549			585,947	620,261
Income/(loss) before income taxes	174,463			167,050			488,266	504,527
Provision/(benefit) for income taxes	41,762			39,195			115,129	118,582
Net income/(loss)	132,701			127,855			373,137	385,945
Average assets	31,626,870			28,551,247			30,224,875	28,339,571
Fixed Income
Segment Reporting Information [Line Items]
Net interest income	5,309			9,054			18,811	26,742
Noninterest income	77,809			41,124			197,238	125,091
Noninterest expense	67,787			46,561			174,331	142,857
Income/(loss) before income taxes	15,331			3,617			41,718	8,976
Provision/(benefit) for income taxes	3,656			719			9,834	1,689
Net income/(loss)	11,675			2,898			31,884	7,287
Average assets	2,882,316			3,246,120			2,952,766	3,322,576
Corporate
Segment Reporting Information [Line Items]
Net interest income	(13,225)			(15,462)			(28,062)	(48,835)
Noninterest income	7,359			222,620			30,111	240,674
Noninterest expense	41,993			33,561			137,867	154,779
Income/(loss) before income taxes	(47,859)			173,597			(135,818)	37,060
Provision/(benefit) for income taxes	(11,550)			40,458			(36,105)	3,719
Net income/(loss)	(36,309)			133,139			(99,713)	33,341
Average assets	6,430,822			6,907,970			7,094,650	6,995,043
Non-Strategic
Segment Reporting Information [Line Items]
Net interest income	6,222			11,009			22,423	40,715
Provision/(provision credit) for loan losses	(5,472)			(5,205)			(14,690)	(15,155)
Noninterest income	791			4,523			3,143	4,989
Noninterest expense	4,681			6,360			6,011	22,167
Income/(loss) before income taxes	7,804			14,377			34,245	38,692
Provision/(benefit) for income taxes	1,928			3,553			8,463	9,563
Net income/(loss)	5,876			10,824			25,782	29,129
Average assets	$ 1,000,893			1,371,696			$ 1,087,283	1,542,297
Visa Class B Shares
Segment Reporting Information [Line Items]
Gain on sale of investments				$ 212,900				$ 212,900