Investment Securities Gross Unrealized Losses and Fair Values of Investments by Category and Length of Time in a Continuous Unrealized Loss Position (Details) $ in Thousands	Sep. 30, 2020 USD ($) Security	Dec. 31, 2019 USD ($) Security
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions \| Security	28	66
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 203,089	$ 334,515
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (1,227)	$ (3,377)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	163	212
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 104,837	$ 253,388
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	(3,864)	(7,706)
Debt Securities, Available-for-sale, Unrealized Loss Position	307,926	587,903
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (5,091)	$ (11,083)
State and Municipal Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions \| Security	6	44
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 25,372	$ 136,344
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (157)	$ (1,024)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 0	$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	25,372	136,344
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (157)	$ (1,024)
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions \| Security	16	5
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 67,030	$ 30,719
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (965)	$ (346)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	1	8
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 6,847	$ 18,759
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	(344)	(1,188)
Debt Securities, Available-for-sale, Unrealized Loss Position	73,877	49,478
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (1,309)	$ (1,534)
Collateralized Mortgage Obligations [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions \| Security	1	5
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 25,489	$ 33,865
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (46)	$ (190)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	0	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 0	$ 5,330
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	(125)
Debt Securities, Available-for-sale, Unrealized Loss Position	25,489	39,195
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (46)	$ (315)
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions \| Security	4	5
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 75,876	$ 12,247
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (57)	$ (40)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	0	26
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 0	$ 127,373
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	(909)
Debt Securities, Available-for-sale, Unrealized Loss Position	75,876	139,620
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (57)	$ (949)
Commercial Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions \| Security	1	7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 9,322	$ 121,340
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (2)	$ (1,777)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 0	$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	9,322	121,340
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (2)	$ (1,777)
Auction Rate Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions \| Security	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 0	$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 0	$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	162	177
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 97,990	$ 101,926
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	(3,520)	(5,484)
Debt Securities, Available-for-sale, Unrealized Loss Position	97,990	101,926
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (3,520)	$ (5,484)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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