Business Segment Information - Amounts Of Consolidated Revenue, Expense, Tax And Assets (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)
Segment Reporting [Abstract]
Number of business segments | segment			4
Segment Reporting Information [Line Items]
Net interest income	$ 305,700	$ 209,817	$ 917,805	$ 600,226
Provision/(provision credit) for loan losses	2,000	0	1,000	(3,000)
Noninterest income	348,972	112,417	612,514	357,029
Noninterest expense	294,031	236,869	940,064	676,991
Income/(loss) before income taxes	358,641	85,365	589,255	283,264
Provision/(benefit) for income taxes	83,925	13,596	133,553	57,903
Net income/(loss)	274,716	71,769	455,702	225,361
Average assets	40,077,033	28,874,827	40,199,487	28,852,679
Loss on sale of equity investments			(212,924)	(5)
Gain on sale of TRUPs loans			(3,777)	0
Visa Class B Shares
Segment Reporting Information [Line Items]
Gain on sale of investments	212,900		212,900
Regional Banking
Segment Reporting Information [Line Items]
Net interest income	302,448	209,100	902,546	604,075
Provision/(provision credit) for loan losses	8,045	8,552	17,428	11,910
Noninterest income	79,857	64,370	240,093	188,089
Noninterest expense	207,591	150,445	619,283	451,135
Income/(loss) before income taxes	166,669	114,473	505,928	329,119
Provision/(benefit) for income taxes	39,101	41,191	118,929	118,771
Net income/(loss)	127,568	73,282	386,999	210,348
Average assets	28,659,158	19,158,852	28,450,747	18,519,999
Fixed Income
Segment Reporting Information [Line Items]
Net interest income	9,048	5,985	26,686	12,126
Noninterest income	41,123	55,803	125,091	161,833
Noninterest expense	47,306	53,136	145,635	155,865
Income/(loss) before income taxes	2,865	8,652	6,142	18,094
Provision/(benefit) for income taxes	532	2,970	988	5,929
Net income/(loss)	2,333	5,682	5,154	12,165
Average assets	3,247,016	2,586,773	3,326,118	2,388,740
Corporate
Segment Reporting Information [Line Items]
Net interest income	(15,415)	(13,769)	(48,651)	(42,408)
Noninterest income	222,619	(9,476)	240,665	2,219
Noninterest expense	33,323	23,926	152,797	65,365
Income/(loss) before income taxes	173,881	(47,171)	39,217	(105,554)
Provision/(benefit) for income taxes	40,529	(34,167)	4,253	(82,758)
Net income/(loss)	133,352	(13,004)	34,964	(22,796)
Average assets	6,904,585	5,697,894	6,990,484	6,421,643
Loss on sale of equity investments		14,300		14,300
Non-Strategic
Segment Reporting Information [Line Items]
Net interest income	9,619	8,501	37,224	26,433
Provision/(provision credit) for loan losses	(6,045)	(8,552)	(16,428)	(14,910)
Noninterest income	5,373	1,720	6,665	4,888
Noninterest expense	5,811	9,362	22,349	4,626
Income/(loss) before income taxes	15,226	9,411	37,968	41,605
Provision/(benefit) for income taxes	3,763	3,602	9,383	15,961
Net income/(loss)	11,463	5,809	28,585	25,644
Average assets	$ 1,266,274	$ 1,431,308	1,432,138	$ 1,522,297
Gain on sale of TRUPs loans			$ 3,800