Consolidated Balance Sheets (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Common stock, par value
Common stock, shares authorized	Unlimited	Unlimited
Common stock, shares issued	89,478,032	87,066,446
Common stock, shares outstanding	89,478,032	87,066,446