Investment Securities (Held-to-Maturity Securities Gross Realized Gains and Losses) (Details) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Realized Gain (Loss) on Held-to-Maturity Securities	$ 0	$ 0	$ 0	$ 0

This item represents the gain (loss) realized on the sale of held-to-maturity securities disposed of during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27405-111563

Name:	us-gaap_HeldtomaturitySecuritiesSoldSecurityRealizedGainLossExcludingOtherThanTemporaryImpairments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration