Loans Past Due Status (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Summarized details of Loans
Current(a)	$ 23,982,264	$ 24,202,209
Nonaccrual(b)(c)	163,292	210,854
Loans and Leases Receivable, Net of Deferred Income, Total	24,162,328	24,451,724
Nonaccrual Loans, Current Portion	$ 99,000	$ 128,000
Percent of current nonaccrual loans	61.00%	61.00%
Financing Receivable, Nonaccrual, Interest Income	$ 0	$ 0
Financing Receivable, Nonaccrual, No Allowance	16,000	28,000
30-59 Days Past Due
Summarized details of Loans
Total Past Due	13,597	18,077
60-89 Days Past Due
Summarized details of Loans
Total Past Due	1,500	18,985
90+ Days Past Due
Summarized details of Loans
Total Past Due	1,675	1,598
PPP
Summarized details of Loans
Current(a)	836,566	767,757
Nonaccrual(b)(c)	0	0
Loans and Leases Receivable, Net of Deferred Income, Total	836,566	767,757
PPP \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	0	0
PPP \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	0	0
PPP \| 90+ Days Past Due
Summarized details of Loans
Total Past Due	0	0
Commercial and industrial
Summarized details of Loans
Current(a)	7,630,593	7,633,269
Nonaccrual(b)(c)	33,192	61,859
Loans and Leases Receivable, Net of Deferred Income, Total	7,664,501	7,701,422
Commercial and industrial \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	444	2,819
Commercial and industrial \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	82	3,300
Commercial and industrial \| 90+ Days Past Due
Summarized details of Loans
Total Past Due	190	175
Commercial real estate — owner occupied
Summarized details of Loans
Current(a)	883,229	899,480
Nonaccrual(b)(c)	7	1,058
Loans and Leases Receivable, Net of Deferred Income, Total	883,237	900,912
Commercial real estate — owner occupied \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	0	158
Commercial real estate — owner occupied \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	0	215
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(a)	9,350,388	9,300,506
Nonaccrual(b)(c)	33,200	62,917
Loans and Leases Receivable, Net of Deferred Income, Total	9,384,303	9,370,091
Commercial and business lending \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	444	2,977
Commercial and business lending \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	82	3,516
Commercial and business lending \| 90+ Days Past Due
Summarized details of Loans
Total Past Due	190	175
Commercial real estate — investor
Summarized details of Loans
Current(a)	4,196,221	4,251,571
Nonaccrual(b)(c)	58,485	78,220
Loans and Leases Receivable, Net of Deferred Income, Total	4,260,706	4,342,584
Commercial real estate — investor \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	5,999	1,024
Commercial real estate — investor \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	0	11,769
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(a)	1,880,995	1,839,073
Nonaccrual(b)(c)	327	353
Loans and Leases Receivable, Net of Deferred Income, Total	1,882,299	1,840,417
Real estate construction \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	977	991
Real estate construction \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	0	0
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(a)	6,077,216	6,090,644
Nonaccrual(b)(c)	58,813	78,573
Loans and Leases Receivable, Net of Deferred Income, Total	6,143,004	6,183,001
Commercial real estate lending \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	6,976	2,015
Commercial real estate lending \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	0	11,769
Commercial real estate lending \| 90+ Days Past Due
Summarized details of Loans
Total Past Due	0	0
Total commercial
Summarized details of Loans
Current(a)	15,427,603	15,391,150
Nonaccrual(b)(c)	92,012	141,490
Loans and Leases Receivable, Net of Deferred Income, Total	15,527,307	15,553,091
Total commercial \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	7,420	4,992
Total commercial \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	82	15,284
Total commercial \| 90+ Days Past Due
Summarized details of Loans
Total Past Due	190	175
Residential mortgage
Summarized details of Loans
Current(a)	7,619,602	7,808,294
Nonaccrual(b)(c)	61,256	59,337
Loans and Leases Receivable, Net of Deferred Income, Total	7,685,218	7,878,324
Residential mortgage \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	3,494	8,975
Residential mortgage \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	479	1,410
Residential mortgage \| 90+ Days Past Due
Summarized details of Loans
Total Past Due	387	308
Home equity
Summarized details of Loans
Current(a)	639,503	692,565
Nonaccrual(b)(c)	9,792	9,888
Loans and Leases Receivable, Net of Deferred Income, Total	651,647	707,255
Home equity \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	2,002	3,071
Home equity \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	350	1,731
Home equity \| 90+ Days Past Due
Summarized details of Loans
Total Past Due	0	0
Other consumer
Summarized details of Loans
Current(a)	295,556	310,200
Nonaccrual(b)(c)	231	140
Loans and Leases Receivable, Net of Deferred Income, Total	298,156	313,054
Other consumer \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	681	1,039
Other consumer \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	589	560
Other consumer \| 90+ Days Past Due
Summarized details of Loans
Total Past Due	1,098	1,115
Total consumer
Summarized details of Loans
Current(a)	8,554,661	8,811,060
Nonaccrual(b)(c)	71,280	69,364
Loans and Leases Receivable, Net of Deferred Income, Total	8,635,020	8,898,632
Total consumer \| 30-59 Days Past Due
Summarized details of Loans
Total Past Due	6,177	13,085
Total consumer \| 60-89 Days Past Due
Summarized details of Loans
Total Past Due	1,417	3,701
Total consumer \| 90+ Days Past Due
Summarized details of Loans
Total Past Due	$ 1,485	$ 1,423

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