Debt Securities Available for Sale - Continuous Unrealized Loss Position of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	$ 75,354	$ 217,762
Less than 12 months, gross unrealized (losses)	(200)	(1,748)
12 months or longer, fair value	88,595	552,442
12 months or longer, gross unrealized (losses)	(1,454)	(18,310)
Fair value	163,949	770,204
Gross unrealized (losses)	(1,654)	(20,058)
U.S. government and agency obligations
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	0	14,668
Less than 12 months, gross unrealized (losses)	0	(202)
12 months or longer, fair value	14,970	29,437
12 months or longer, gross unrealized (losses)	(22)	(515)
Fair value	14,970	44,105
Gross unrealized (losses)	(22)	(717)
Mortgage-backed securities and collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	70,393	176,614
Less than 12 months, gross unrealized (losses)	(161)	(1,034)
12 months or longer, fair value	59,713	509,397
12 months or longer, gross unrealized (losses)	(343)	(16,402)
Fair value	130,106	686,011
Gross unrealized (losses)	(504)	(17,436)
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	4,961	26,480
Less than 12 months, gross unrealized (losses)	(39)	(512)
12 months or longer, fair value	9,371	9,358
12 months or longer, gross unrealized (losses)	(630)	(643)
Fair value	14,332	35,838
Gross unrealized (losses)	(669)	(1,155)
Trust preferred securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, fair value	0	0
Less than 12 months, gross unrealized (losses)	0	0
12 months or longer, fair value	4,541	4,250
12 months or longer, gross unrealized (losses)	(459)	(750)
Fair value	4,541	4,250
Gross unrealized (losses)	$ (459)	$ (750)

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 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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