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Fair Value Measurements - Changes in Level 3 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Collateralized loan obligations
Changes in Level 3
Beginning balance	$ 2,268	$ 3,119
Transfers out of Level 3	(1,308)
Total gains or losses
Included in earnings (or changes in net assets)	35	40
Included in other comprehensive income	40	21
Purchases, issuances, sales, and settlements
Settlements	(1,035)	(912)
Ending balance		2,268
States and political subdivisions
Changes in Level 3
Beginning balance	14,261	22,226
Total gains or losses
Included in other comprehensive income	(746)	(796)
Purchases, issuances, sales, and settlements
Purchases	22,046	16,712
Settlements	(27,396)	(23,881)
Ending balance	8,165	14,261
Mortgage servicing rights
Changes in Level 3
Beginning balance	6,944	6,489
Total gains or losses
Included in earnings (or changes in net assets)	(181)	(270)
Purchases, issuances, sales, and settlements
Issuances	1,146	1,257
Settlements	(552)	(532)
Ending balance	$ 7,357	$ 6,944

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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 transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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