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Fair Value Measurements - Changes in Level 3 (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Changes in Level 3
Beginning balance		$ 2,268
Total gains or losses
Included in other comprehensive income		28
Purchases, issuances, sales, and settlements
Settlements		(213)
Ending balance		2,096
Changes in Level 3 (liabilities)
Included in earnings (or changes in net assets)		13
US States and Political Subdivisions Debt Securities [Member]
Changes in Level 3
Beginning balance	$ 8,165	14,261
Total gains or losses
Included in other comprehensive income	171	(699)
Purchases, issuances, sales, and settlements
Purchases	11,325	13,085
Settlements	(97)	(120)
Ending balance	19,556	26,527
Changes in Level 3 (liabilities)
Included in earnings (or changes in net assets)	(8)
Mortgage Servicing Rights [Member]
Changes in Level 3
Beginning balance	7,357	6,944
Total gains or losses
Included in earnings (or changes in net assets)		417
Purchases, issuances, sales, and settlements
Issuances	177	291
Settlements	(98)	(111)
Ending balance	6,715	$ 7,541
Changes in Level 3 (liabilities)
Included in earnings (or changes in net assets)	$ (721)

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of gain (loss) recognized on the income statement for financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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