Investments in Qualified Affordable Housing Projects Investments in Qualified Affordable Housing Projects - Narrative (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Carrying value of qualified affordable housing project investments	$ 7,232,000	$ 7,637,000
Funding obligation related to qualified affordable housing projects	$ 0

Amount of commitment or contingent commitments to qualified affordable housing project investments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 740
-Section 50
-Paragraph 2
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=64813897&loc=SL49122993-202985

Name:	us-gaap_QualifiedAffordableHousingProjectInvestmentsCommitment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant