Capital Stock (Details) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) vote shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)
Capital [Abstract]
Authorized share capital (in shares) | shares		233,333,000	233,333,000
Number of votes per share		1
Shareholder ownership threshold for voting rights (as a percent)		9.50%
Maximum number of votes per share for certain shareholders under 9.5% shareholder provision		1
Minimum number of votes per share for other shareholders under 9.5% shareholder provision		1
Common shares, issued (in shares) | shares	5,000,000.0	98,394,000	98,139,000
Share price (in dollars per share) | $ / shares	$ 39.90
Net proceeds from sale of stock | $	$ 197,700	$ 0	$ 0	$ 197,829