Consolidated Balance Sheets (Parenthetical) - shares	Dec. 31, 2017	Dec. 31, 2016
Class A Subordinate Voting
Common shares issued (in shares)	87,067,604	77,030,952
Common shares outstanding (in shares)	87,067,604	77,030,952
Class B Multiple Voting
Common shares issued (in shares)	12,810,084	12,374,528
Common shares outstanding (in shares)	12,810,084	12,374,528

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant