Segment Reporting (Details) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2020 USD ($) employee	Mar. 31, 2020 segment	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) employee	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) employee
Segment Reporting [Abstract]
Number of reportable segments | segment		3
Income Statement Related Disclosures [Abstract]
Net interest income	$ 376,566		$ 397,262	$ 749,826	$ 794,438
Non-interest revenue	173,484		89,807	277,341	169,185
Non-interest expense	284,141		264,126	560,421	556,537
Pre-provision net revenue	265,909			466,746
Balance Sheet Related Disclosures [Abstract]
Loans, net of deferred fees and costs	39,914,297			39,914,297		$ 37,162,450
Total deposits	$ 44,194,580			$ 44,194,580		$ 38,405,504
Total full-time equivalent employees | employee	5,308			5,308		5,264
Operating Segments | Community Banking
Income Statement Related Disclosures [Abstract]
Net interest income	$ 220,638			$ 417,885
Non-interest revenue	25,982			59,431
Non-interest expense	75,984			151,288
Pre-provision net revenue	170,636			326,028
Balance Sheet Related Disclosures [Abstract]
Loans, net of deferred fees and costs	11,837,955			11,837,955		$ 12,170,914
Total deposits	$ 28,777,901			$ 28,777,901		$ 25,610,777
Total full-time equivalent employees | employee	2,273			2,273		2,301
Operating Segments | Wholesale Banking
Income Statement Related Disclosures [Abstract]
Net interest income	$ 145,016			$ 268,185
Non-interest revenue	5,654			14,910
Non-interest expense	22,934			41,136
Pre-provision net revenue	127,736			241,959
Balance Sheet Related Disclosures [Abstract]
Loans, net of deferred fees and costs	18,718,503			18,718,503		$ 17,643,509
Total deposits	$ 9,737,901			$ 9,737,901		$ 8,314,184
Total full-time equivalent employees | employee	269			269		213
Operating Segments | Financial Management Services
Income Statement Related Disclosures [Abstract]
Net interest income	$ 18,832			$ 35,614
Non-interest revenue	52,972			100,247
Non-interest expense	48,281			91,570
Pre-provision net revenue	23,523			44,291
Balance Sheet Related Disclosures [Abstract]
Loans, net of deferred fees and costs	5,544,768			5,544,768		$ 5,285,455
Total deposits	$ 313,296			$ 313,296		$ 284,716
Total full-time equivalent employees | employee	831			831		839
Treasury and Corporate Other
Income Statement Related Disclosures [Abstract]
Net interest income	$ (7,920)			$ 28,142
Non-interest revenue	88,876			102,753
Non-interest expense	136,942			276,427
Pre-provision net revenue	(55,986)			(145,532)
Balance Sheet Related Disclosures [Abstract]
Loans, net of deferred fees and costs	3,813,071			3,813,071		$ 2,062,572
Total deposits	$ 5,365,482			$ 5,365,482		$ 4,195,827
Total full-time equivalent employees | employee	1,935			1,935		1,911
Proforma
Income Statement Related Disclosures [Abstract]
Net interest income			397,262		794,438
Non-interest revenue			89,807		169,185
Non-interest expense			264,126		556,537
Pre-provision net revenue			222,943		407,086
Proforma | Operating Segments | Community Banking
Income Statement Related Disclosures [Abstract]
Net interest income			207,493		422,253
Non-interest revenue			34,050		66,826
Non-interest expense			73,910		148,727
Pre-provision net revenue			167,633		340,352
Proforma | Operating Segments | Wholesale Banking
Income Statement Related Disclosures [Abstract]
Net interest income			128,857		254,468
Non-interest revenue			7,937		14,695
Non-interest expense			14,709		29,728
Pre-provision net revenue			122,085		239,435
Proforma | Operating Segments | Financial Management Services
Income Statement Related Disclosures [Abstract]
Net interest income			30,978		59,843
Non-interest revenue			38,628		70,907
Non-interest expense			37,508		70,726
Pre-provision net revenue			32,098		60,024
Proforma | Treasury and Corporate Other
Income Statement Related Disclosures [Abstract]
Net interest income			29,934		57,874
Non-interest revenue			9,192		16,757
Non-interest expense			137,999		307,356
Pre-provision net revenue			$ (98,873)		$ (232,725)