Allowance for Credit Losses - Loans on Nonaccrual Status and Loans Past Due 90 Days or More and Still Accruing (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual		$ 146,774	$ 54,057
End of Period Nonaccrual	$ 111,312	111,312	146,774
Nonaccrual With No Related Allowance	65,145	65,145	71,410
Past Due 90+ Days Still Accruing			503
Interest income recognized on nonaccrual	642	1,383	826
Commercial
Financing Receivable, Nonaccrual [Line Items]
Non - performing	1,700	1,700
Commercial | Commercial real estate
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual		101,070	25,356
End of Period Nonaccrual	54,797	54,797	101,070
Nonaccrual With No Related Allowance	47,730	47,730	60,401
Past Due 90+ Days Still Accruing			0
Interest income recognized on nonaccrual	493	556	22
Commercial | Commercial and industrial
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual		16,985	10,911
End of Period Nonaccrual	33,909	33,909	16,985
Nonaccrual With No Related Allowance	12,566	12,566	6,436
Past Due 90+ Days Still Accruing			0
Interest income recognized on nonaccrual	6	88	101
Commercial | Commercial construction
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual		384	737
End of Period Nonaccrual	4,053	4,053	384
Nonaccrual With No Related Allowance	3,357	3,357	285
Past Due 90+ Days Still Accruing			0
Interest income recognized on nonaccrual	0	0	0
Commercial | Business banking
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual		17,122	9,863
End of Period Nonaccrual	10,221	10,221	17,122
Nonaccrual With No Related Allowance	1,492	1,492	3,890
Past Due 90+ Days Still Accruing			371
Interest income recognized on nonaccrual	57	333	275
Consumer | Consumer real estate
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual		11,117	6,063
End of Period Nonaccrual	8,143	8,143	11,117
Nonaccrual With No Related Allowance	0	0	398
Past Due 90+ Days Still Accruing			132
Interest income recognized on nonaccrual	86	405	423
Consumer | Other consumer
Financing Receivable, Nonaccrual [Line Items]
Beginning of Period Nonaccrual		96	1,127
End of Period Nonaccrual	189	189	96
Nonaccrual With No Related Allowance	0	0	0
Past Due 90+ Days Still Accruing			0
Interest income recognized on nonaccrual	$ 0	$ 1	$ 4