Segment Reporting (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) employee	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) employee segment	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) employee
Segment Reporting [Abstract]
Number of reportable segments | segment			3
Income Statement Related Disclosures [Abstract]
Net interest income	$ 376,990	$ 402,097	$ 1,126,816	$ 1,196,535
Non-interest revenue	114,411	88,760	391,752	257,945
Non-interest expense	316,655	276,310	877,076	832,847
Pre-provision net revenue	174,746		641,492
Balance Sheet Related Disclosures [Abstract]
Loans, net of deferred fees and costs	39,549,847		39,549,847		$ 37,162,450
Total deposits	$ 44,665,904		$ 44,665,904		$ 38,405,504
Total full-time equivalent employees | employee	5,232		5,232		5,264
Operating Segments | Community Banking
Income Statement Related Disclosures [Abstract]
Net interest income	$ 220,426		$ 638,311
Non-interest revenue	29,982		89,413
Non-interest expense	68,571		219,859
Pre-provision net revenue	181,837		507,865
Balance Sheet Related Disclosures [Abstract]
Loans, net of deferred fees and costs	11,489,106		11,489,106		$ 12,170,914
Total deposits	$ 28,870,928		$ 28,870,928		$ 25,610,777
Total full-time equivalent employees | employee	2,200		2,200		2,301
Operating Segments | Wholesale Banking
Income Statement Related Disclosures [Abstract]
Net interest income	$ 139,080		$ 407,265
Non-interest revenue	5,496		20,406
Non-interest expense	19,530		63,176
Pre-provision net revenue	125,046		364,495
Balance Sheet Related Disclosures [Abstract]
Loans, net of deferred fees and costs	19,204,961		19,204,961		$ 17,643,509
Total deposits	$ 10,339,568		$ 10,339,568		$ 8,314,184
Total full-time equivalent employees | employee	285		285		213
Operating Segments | Financial Management Services
Income Statement Related Disclosures [Abstract]
Net interest income	$ 20,986		$ 56,600
Non-interest revenue	65,820		166,067
Non-interest expense	92,931		184,501
Pre-provision net revenue	(6,125)		38,166
Balance Sheet Related Disclosures [Abstract]
Loans, net of deferred fees and costs	5,412,944		5,412,944		$ 5,285,455
Total deposits	$ 414,243		$ 414,243		$ 284,716
Total full-time equivalent employees | employee	843		843		839
Treasury and Corporate Other
Income Statement Related Disclosures [Abstract]
Net interest income	$ (3,502)		$ 24,640
Non-interest revenue	13,113		115,866
Non-interest expense	135,623		409,540
Pre-provision net revenue	(126,012)		(269,034)
Balance Sheet Related Disclosures [Abstract]
Loans, net of deferred fees and costs	3,442,836		3,442,836		$ 2,062,572
Total deposits	$ 5,041,165		$ 5,041,165		$ 4,195,827
Total full-time equivalent employees | employee	1,904		1,904		1,911
Proforma
Income Statement Related Disclosures [Abstract]
Net interest income		402,097		1,196,535
Non-interest revenue		88,760		257,945
Non-interest expense		276,310		832,847
Pre-provision net revenue		214,547		621,633
Proforma | Operating Segments | Community Banking
Income Statement Related Disclosures [Abstract]
Net interest income		203,197		625,450
Non-interest revenue		35,145		101,971
Non-interest expense		76,414		225,141
Pre-provision net revenue		161,928		502,280
Proforma | Operating Segments | Wholesale Banking
Income Statement Related Disclosures [Abstract]
Net interest income		133,773		388,241
Non-interest revenue		7,092		21,787
Non-interest expense		25,413		55,141
Pre-provision net revenue		115,452		354,887
Proforma | Operating Segments | Financial Management Services
Income Statement Related Disclosures [Abstract]
Net interest income		26,582		86,425
Non-interest revenue		40,966		111,873
Non-interest expense		40,413		111,139
Pre-provision net revenue		27,135		87,159
Proforma | Treasury and Corporate Other
Income Statement Related Disclosures [Abstract]
Net interest income		38,545		96,419
Non-interest revenue		5,557		22,314
Non-interest expense		134,070		441,426
Pre-provision net revenue		$ (89,968)		$ (322,693)