Mortgage Servicing Rights (Narrative) (Details 1) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Transfers and Servicing of Financial Assets [Abstract]
Residential Mortgage Loans Serviced for Third Parties	$ 2,900.0	$ 2,700.0	$ 2,700.0
Servicing income, including late and ancillary fees	$ 7.1	$ 6.9	$ 7.2

The total amount of contractually specified servicing fees, late fees, and ancillary fees earned for each period for which results of operations are presented.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122596-111746

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