Recent Accounting Developments (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201708Member
Allowance for credit losses	$ 388,971	$ 163,273			$ 158,461
Allowance for loan losses	388,908	163,273	$ 373,109		158,461	$ 161,901	$ 154,164
Allowance for held-to-maturity securities losses	63	0			0
Financial assets held at amortized cost, accrued interest	116,900
Cumulative effect adjustment from the adoption of ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses				$ 47,400
Allowance for loan losses					47,344
Allowance for held-to-maturity securities losses				74
Loans acquired with deteriorated credit quality
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses		473
Loans acquired with deteriorated credit quality | Cumulative effect adjustment from the adoption of ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses				11,000
Loans acquired without deteriorated credit quality | Cumulative effect adjustment from the adoption of ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses				3,200
Unfunded lending-related commitments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses	62,949	1,510			1,633
Unfunded lending-related commitments | Cumulative effect adjustment from the adoption of ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses				33,200
Loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses	$ 325,959	$ 161,763			$ 156,828
Loans | Cumulative effect adjustment from the adoption of ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses				$ 14,200