Shareholders Equity - Narrative (Details) - Normal Course Issuer Bid (NCIB) [Member] - shares	6 Months Ended
Jun. 30, 2018	May 10, 2017
Share repurchase expiration date	May 14, 2018
Maximum [Member]
Common shares authorized to be repurchased (in shares)		4,380,000

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

No definition available.

Name:	us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant