Investment Securities - Narrative (Details) - Investment Securities [Member] - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Average percent of amortized cost for securities in unrealized loss positions for more than 12 months	99.50%
Other-than-temporary impairment	$ 0	$ 0

Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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

Name:	us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration