Derivative Financial Instruments (AOCL Cash Flow Derivatives - Narrative) (Details) - Cash Flow Hedging [Member] $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Derivative [Line Items]
Cash flow hedge to be reclassified from AOCL as an increase to interest expense	$ (6.2)
Remaining unamortized loss on termination of cash flow hedges	14.9
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Cash flow hedge to be reclassified from AOCL as an increase to interest expense	$ 0.8

The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994

Name:	us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant