Variable Interest Entities (Narrative) (Details) - LIHTC Investments [Member]	3 Months Ended
Mar. 31, 2018
Minimum [Member]
Variable Interest Entity [Line Items]
Commitment, expected payment date	2018
Maximum [Member]
Variable Interest Entity [Line Items]
Commitment, expected payment date	2021

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_VariableInterestEntityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration