Derivatives (Net Gains (Losses) on Derivatives Designated as Hedges) (Details) - Interest Expense - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Certificates of deposits
Derivative [Line Items]
Recognized on certificates of deposit	$ 2,271	$ 157	$ (3,190)
Interest rate swaps on certificates of deposit
Derivative [Line Items]
Recognized on interest rate swaps	$ (2,734)	$ (794)	$ 3,452

Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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- Definition

Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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- Definition

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