Shareholders Equity - Narrative (Details) - shares	9 Months Ended
	Sep. 30, 2018	Oct. 17, 2018	May 10, 2017
Normal Course Issuer Bid (NCIB) [Member]
Share repurchase expiration date	May 14, 2018
Normal Course Issuer Bid (NCIB) [Member] | Maximum [Member]
Common shares authorized to be repurchased (in shares)			4,380,000
Subsequent Event [Member] | Current Normal Course Issuer Bid (NCIB) [Member] | Maximum [Member]
Common shares authorized to be repurchased (in shares)		5,680,000