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	Mar. 31, 2021 USD ($) Security	Dec. 31, 2020 USD ($) Security
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions \| Security	48	22
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 542,485	$ 266,636
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (14,408)	$ (1,660)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	120	163
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 91,532	$ 105,077
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(325)	(3,618)
Debt Securities, Available-for-sale, Unrealized Loss Position	634,017	371,713
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (14,733)	$ (5,278)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions \| Security	33
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 573,076
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (25,973)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	0
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	573,076
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	$ (25,973)
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	21
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 88,141
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (1,253)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Debt Securities, Available-for-sale, Unrealized Loss Position	88,141
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (1,253)
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	7	9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 41,956	$ 44,528
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (582)	$ (377)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	2	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 15,328	$ 6,871
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(179)	(314)
Debt Securities, Available-for-sale, Unrealized Loss Position	57,284	51,399
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (761)	$ (691)
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	2	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 55,305	$ 57,601
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (1,005)	$ (115)
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, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	55,305	57,601
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (1,005)	$ (115)
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	8	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 173,908	$ 20,124
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (3,986)	$ (27)
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, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	173,908	20,124
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (3,986)	$ (27)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions \| Security	12
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 205,072
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (8,025)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	0
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	205,072
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	$ (8,025)
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	10	9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 183,175	$ 144,383
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (7,582)	$ (1,141)
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, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	183,175	144,383
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (7,582)	$ (1,141)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions \| Security	21
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	$ 368,004
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (17,948)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions \| Security	0
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	368,004
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	$ (17,948)
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	118	162
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	$ 76,204	$ 98,206
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(146)	(3,304)
Debt Securities, Available-for-sale, Unrealized Loss Position	76,204	98,206
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (146)	$ (3,304)

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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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