Fair Value Measurements and Derivative Instruments Reporting (Narrative) (Details) $ in Millions	Jun. 30, 2018 CAD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value Measurements And Derivative Instruments Reporting [Abstract]
Assets measured at fair value on a nonrecurring basis		$ 0
Fair value of land lease	$ 28.6	21,700,000
Cash equivalents		$ 0	$ 0

Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant