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Fair Value Measurements - Changes in Level 3 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Interest rate swap agreements net of swap credit valuation
Changes in Level 3 (liabilities)
Beginning balance		$ (6)
Included in earnings (or changes in net assets)		6
Asset-backed securities
Changes in Level 3
Beginning balance	$ 52,941	154,137
Total gains or losses
Included in earnings (or changes in net assets)	(28)	3,556
Included in other comprehensive income	(541)	(1,454)
Purchases, issuances, sales, and settlements
Purchases		63,704
Sales	(27,455)	(167,002)
Ending balance		52,941
Transfers out of Level 3	(24,917)
States and political subdivisions
Changes in Level 3
Beginning balance	118	125
Purchases, issuances, sales, and settlements
Settlements	(7)	(7)
Ending balance	111	118
Mortgage servicing rights
Changes in Level 3
Beginning balance	5,462	5,807
Total gains or losses
Included in earnings (or changes in net assets)	(466)	(1,214)
Purchases, issuances, sales, and settlements
Issuances	1,526	869
Settlements	(675)
Ending balance	$ 5,847	$ 5,462

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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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-Name Accounting Standards Codification
-Topic 820
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-Section 50
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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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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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