CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Unrealized holding (loss)/gain on securities arising during the period, income tax expense (benefit)	$ (3,900)	$ (1,600)	$ 714
Reclassification adjustment for net (gains) losses on sale of securities included in net income, income tax expense (benefit)	$ 1	$ (97)	$ 0

Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580

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