Condensed Consolidated Statements of Shareholders' Equity (Parenthetical) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Condensed Consolidated Statements of Shareholders' Equity [Abstract]
Cumulative effect adjustment attributable to investment in Telesat, tax expense (benefit)	$ (5.9)

Amount of the related income tax effect of a cumulative effect on retained earnings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22663-107794

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