Investment Securities - Schedule of unrealized loss on investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 237,613	$ 506,280
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,106	5,998
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	171,805	449,569
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5,117	19,917
Debt Securities, Available-for-sale, Unrealized Loss Position	409,418	955,849
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	6,223	25,915
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value		124,616
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		1,933
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		77,654
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		1,742
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		202,270
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		3,675
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	237,613	506,280
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,106	5,998
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	171,805	449,569
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5,117	19,917
Debt Securities, Available-for-sale, Unrealized Loss Position	409,418	955,849
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 6,223	25,915
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value		32,656
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		838
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		6,931
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		165
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		39,587
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		1,003
Obligations of States and Political Subdivisions
Investment [Line Items]
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value		91,960
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		1,095
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		70,723
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		1,577
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		162,683
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		$ 2,672

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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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