Derivative Instruments - Gains (Losses) On Derivative Financial Instruments (Details) - Not designated as hedging instruments: - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Derivatives, Fair Value [Line Items]
Gains (losses) on derivative financial instruments	$ 3,258	$ (2,337)
Interest rate contracts \| Included in interest income on loans
Derivatives, Fair Value [Line Items]
Gains (losses) on derivative financial instruments	986	679
Interest rate lock commitments \| Included in mortgage banking income
Derivatives, Fair Value [Line Items]
Gains (losses) on derivative financial instruments	2,184	2,853
Forward commitments \| Included in mortgage banking income
Derivatives, Fair Value [Line Items]
Gains (losses) on derivative financial instruments	$ 88	$ (5,869)

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration