Investment Securities - Additional Information (Details)	3 Months Ended
Mar. 31, 2020 USD ($) Security	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Other-than-temporary impairment charges	$ 0	$ 0
Percentage of fair value of securities in investment portfolio reflect unrealized loss	6.00%		35.00%
Number of securities in a loss position for more than twelve months \| Security	10
Number of securities in a loss position for less than twelve months \| Security	17
Allowance for credit losses related to available-for-sale securities	$ 0
Collateral Pledged
Schedule Of Available For Sale Securities [Line Items]
Carrying value of securities pledged	$ 728,700,000		$ 629,400,000

Percentage of fair value of securities in investment portfolio reflect unrealized loss.

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- Definition

Number of investment positions in available-for-sale investments in a continuous unrealized loss position for less than one year or normal operating cycle, if longer, for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

+ References

No definition available.

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- Definition

Number of investment positions in available-for-sale investments that have been in a continuous unrealized loss position for greater than or equal to a year for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

+ References

No definition available.

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- Definition

Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (a)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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-Section 50
-Paragraph 9
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-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922900-210455

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

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- Definition

Amount of restricted investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
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The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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