Summary of Significant Accounting Policies (Discontinued Operations) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Interest allocated to discontinued operations	$ 0.2	$ 0.4	$ 0.2

Amount of interest expense attributable to disposal group, including, but not limited to, discontinued operation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section S99
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=26872618&loc=d3e7436-122677

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721673-107760

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=65878427&loc=d3e1063-107759

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=65878427&loc=d3e1060-107759

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