Earnings per share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings per share
Net (loss) income	$ (59)	$ 15
Weighted average number of common shares outstanding - basic (in shares)	59.5	56.4
Weighted dilutive effect of equity awards		0.3
Weighted average number of common shares outstanding-diluted	59.5	56.7
Earnings per common share:
Basic (In dollars per share)	$ (0.99)	$ 0.27
Diluted (In dollars per share)	$ (0.99)	$ 0.26