Investments - Investment Securities Continuous Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Marketable Securities [Line Items]
Held-to-Maturity, Fair Value of Investments with Unrealized Losses, Less Than 12 Months		$ 21,074
Held-to-Maturity, Gross Unrealized Losses, Less Than 12 Months		193
Held-to-Maturity, Fair Value of Investments with Unrealized Losses, 12 Months or Greater		3,311
Held-to-Maturity, Gross Unrealized Losses, 12 Months or Greater		13
Held-to-Maturity, Fair Value of Investments with Unrealized Losses, Total		24,385
Held-to-Maturity, Gross Unrealized Losses, Total	$ 935	206
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months	29,845	23,573
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	329	122
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater		18,220
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater		43
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	29,845	41,793
Available-for Sale, Gross Unrealized Losses, Total	329	165
Fair Value of Investments with Unrealized Losses, Less Than 12 months		44,647
Gross Unrealized Loss, Less Than 12 Months		315
Fair Value of Investments with Unrealized Losses, 12 Months or Greater		21,531
Gross Unrealized Losses, 12 Months or Greater		56
Fair Value of Investments with Unrealized Losses, Total		66,178
Gross Unrealized Losses, Total		371
States and Political Subdivisions [Member]
Marketable Securities [Line Items]
Held-to-Maturity, Fair Value of Investments with Unrealized Losses, Less Than 12 Months		21,074
Held-to-Maturity, Gross Unrealized Losses, Less Than 12 Months		193
Held-to-Maturity, Fair Value of Investments with Unrealized Losses, Total		21,074
Held-to-Maturity, Gross Unrealized Losses, Total	145	193
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months	6,260	4,140
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	6	26
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	6,260	4,140
Available-for Sale, Gross Unrealized Losses, Total	6	26
Corporate Bonds [Member]
Marketable Securities [Line Items]
Held-to-Maturity, Gross Unrealized Losses, Total	790
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months	23,585	6,426
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	323	1
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	23,585	6,426
Available-for Sale, Gross Unrealized Losses, Total	$ 323	1
U.S. Agency-Based Mortgage-Backed Securities [Member]
Marketable Securities [Line Items]
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months		13,007
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months		95
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater		1,152
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater		1
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total		14,159
Available-for Sale, Gross Unrealized Losses, Total		96
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Marketable Securities [Line Items]
Held-to-Maturity, Fair Value of Investments with Unrealized Losses, 12 Months or Greater		3,243
Held-to-Maturity, Gross Unrealized Losses, 12 Months or Greater		12
Held-to-Maturity, Fair Value of Investments with Unrealized Losses, Total		3,243
Held-to-Maturity, Gross Unrealized Losses, Total		12
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater		17,068
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater		42
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total		17,068
Available-for Sale, Gross Unrealized Losses, Total		42
Asset-Backed Securities [Member]
Marketable Securities [Line Items]
Held-to-Maturity, Fair Value of Investments with Unrealized Losses, 12 Months or Greater		68
Held-to-Maturity, Gross Unrealized Losses, 12 Months or Greater		1
Held-to-Maturity, Fair Value of Investments with Unrealized Losses, Total		68
Held-to-Maturity, Gross Unrealized Losses, Total		$ 1

Continuous unrealized loss position greater than twelve months aggregate losses.

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Continuous unrealized loss position greater than twelve months fair value.

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Securities continuous unrealized loss position aggregate losses.

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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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