Investment securities - Schedule of Gross Unrealized Losses (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Abstract]
Debt securities, available-for-sale, unrealized loss, less than 12 months, fair value	$ 18,515	$ 63,074
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(269)	(394)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, fair value	0	175,730
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	0	(1,497)
Debt securities, available-for-sale, continuous unrealized loss position, fair value	18,515	238,804
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(269)	(1,891)
Mortgage-backed securities - residential
Debt Securities, Available-for-sale [Abstract]
Debt securities, available-for-sale, unrealized loss, less than 12 months, fair value	14,746	47,641
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(7)	(164)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, fair value	0	175,730
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	0	(1,497)
Debt securities, available-for-sale, continuous unrealized loss position, fair value	14,746	223,371
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(7)	(1,661)
Municipals, tax exempt
Debt Securities, Available-for-sale [Abstract]
Debt securities, available-for-sale, unrealized loss, less than 12 months, fair value	2,784	15,433
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(247)	(230)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, fair value	0	0
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	0	0
Debt securities, available-for-sale, continuous unrealized loss position, fair value	2,784	15,433
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(247)	$ (230)
Corporate securities
Debt Securities, Available-for-sale [Abstract]
Debt securities, available-for-sale, unrealized loss, less than 12 months, fair value	985
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(15)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, fair value	0
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	0
Debt securities, available-for-sale, continuous unrealized loss position, fair value	985
Debt securities, available-for-sale, unrealized loss position, accumulated loss	$ (15)

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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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Amount of accumulated unrealized loss on 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 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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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 less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on 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 less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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

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