Loans, Loans by Past Due Status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Summarized details of Loans
Current	$ 24,202,209	$ 22,679,696
Financing Receivable, Recorded Investment, Nonaccrual Status	210,854	118,380
Loans	24,451,724	22,821,440
Financing Receivable, Nonaccrual, Interest Income	0
Financing Receivable, Nonaccrual, No Allowance	140,000
30-59 Days Past Due
Summarized details of Loans
Total Past Due	18,077	18,188
60-89 Days Past Due
Summarized details of Loans
Total Past Due	18,985	2,916
90+ Days Past Due
Summarized details of Loans
Total Past Due	1,598	2,259
PPP
Summarized details of Loans
Current	767,757
Financing Receivable, Recorded Investment, Nonaccrual Status	0
Loans	767,757	0
PPP | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	0
PPP | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	0
PPP | 90+ Days Past Due
Summarized details of Loans
Total Past Due	0
Commercial and industrial
Summarized details of Loans
Current	7,633,269	7,307,118
Financing Receivable, Recorded Investment, Nonaccrual Status	61,859	46,312
Loans	7,701,422	7,354,594
Commercial and industrial | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	2,819	576
Commercial and industrial | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	3,300	245
Commercial and industrial | 90+ Days Past Due
Summarized details of Loans
Total Past Due	175	342
Commercial real estate - owner occupied
Summarized details of Loans
Current	899,480	909,828
Financing Receivable, Recorded Investment, Nonaccrual Status	1,058	67
Loans	900,912	911,265
Commercial real estate - owner occupied | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	158	1,369
Commercial real estate - owner occupied | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	215	0
Commercial real estate - owner occupied | 90+ Days Past Due
Summarized details of Loans
Total Past Due	0	0
Commercial and business lending
Summarized details of Loans
Current	9,300,506	8,216,947
Financing Receivable, Recorded Investment, Nonaccrual Status	62,917	46,380
Loans	9,370,091	8,265,858
Commercial and business lending | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	2,977	1,945
Commercial and business lending | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	3,516	245
Commercial and business lending | 90+ Days Past Due
Summarized details of Loans
Total Past Due	175	342
Commercial real estate - investor
Summarized details of Loans
Current	4,251,571	3,788,296
Financing Receivable, Recorded Investment, Nonaccrual Status	78,220	4,409
Loans	4,342,584	3,794,517
Commercial real estate - investor | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	1,024	1,812
Commercial real estate - investor | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	11,769	0
Commercial real estate - investor | 90+ Days Past Due
Summarized details of Loans
Total Past Due	0	0
Real estate construction
Summarized details of Loans
Current	1,839,073	1,420,310
Financing Receivable, Recorded Investment, Nonaccrual Status	353	493
Loans	1,840,417	1,420,900
Real estate construction | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	991	64
Real estate construction | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	0	33
Real estate construction | 90+ Days Past Due
Summarized details of Loans
Total Past Due	0	0
Commercial real estate lending
Summarized details of Loans
Current	6,090,644	5,208,606
Financing Receivable, Recorded Investment, Nonaccrual Status	78,573	4,902
Loans	6,183,001	5,215,417
Commercial real estate lending | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	2,015	1,876
Commercial real estate lending | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	11,769	33
Commercial real estate lending | 90+ Days Past Due
Summarized details of Loans
Total Past Due	0	0
Total commercial
Summarized details of Loans
Current	15,391,150	13,425,552
Financing Receivable, Recorded Investment, Nonaccrual Status	141,490	51,282
Loans	15,553,091	13,481,275
Total commercial | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	4,992	3,821
Total commercial | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	15,284	278
Total commercial | 90+ Days Past Due
Summarized details of Loans
Total Past Due	175	342
Residential mortgage
Summarized details of Loans
Current	7,808,294	8,069,863
Financing Receivable, Recorded Investment, Nonaccrual Status	59,337	57,844
Loans	7,878,324	8,136,980
Residential mortgage | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	8,975	8,749
Residential mortgage | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	1,410	525
Residential mortgage | 90+ Days Past Due
Summarized details of Loans
Total Past Due	308	0
Home equity
Summarized details of Loans
Current	692,565	837,274
Financing Receivable, Recorded Investment, Nonaccrual Status	9,888	9,104
Loans	707,255	852,025
Home equity | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	3,071	4,483
Home equity | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	1,731	1,164
Home equity | 90+ Days Past Due
Summarized details of Loans
Total Past Due	0	0
Other consumer
Summarized details of Loans
Current	310,200	347,007
Financing Receivable, Recorded Investment, Nonaccrual Status	140	152
Loans	313,054	351,159
Other consumer | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	1,039	1,135
Other consumer | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	560	949
Other consumer | 90+ Days Past Due
Summarized details of Loans
Total Past Due	1,115	1,917
Total consumer
Summarized details of Loans
Current	8,811,060	9,254,144
Financing Receivable, Recorded Investment, Nonaccrual Status	69,364	67,099
Loans	8,898,632	9,340,164
Total consumer | 30-59 Days Past Due
Summarized details of Loans
Total Past Due	13,085	14,366
Total consumer | 60-89 Days Past Due
Summarized details of Loans
Total Past Due	3,701	2,638
Total consumer | 90+ Days Past Due
Summarized details of Loans
Total Past Due	$ 1,423	$ 1,917