Share-based compensation plans (Tables)

6 Months Ended

Jun. 30, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of assumptions

2009 share award and incentive plan	Class A common shares	Date granted	Vesting date	Exercise price	Expected share price volatility	Risk-free interest rate	Expected dividends per share	Expected life of awards
Share options	40,900	June 11, 2017	June 11, 2018	$13.45	29%	1.50%	$—	2.5 years
Share options	40,900	June 11, 2017	June 11, 2019	$13.45	29%	1.50%	$—	3.5 years
Share options	40,900	June 11, 2017	June 11, 2020	$13.45	30%	1.77%	$—	4.5 years
Share options	40,900	June 11, 2017	June 11, 2021	$13.45	34%	1.77%	$—	5.5 years

During the six months endedJune 30, 2017, the following restricted share awards were made under the 2009 share award and incentive plan on the following dates:

2009 share award and incentive plan	Class A common shares	Date granted	Vesting date	Purchase price
Restricted shares without performance criteria	116,540	June 11, 2017	Directors to elect	$0.01
Restricted shares without performance criteria	34,450	March 17, 2017	March 17, 2018	$0.01
Restricted shares without performance criteria	34,450	March 17, 2017	March 17, 2019	$0.01
Restricted shares without performance criteria	117,231	March 17, 2017	March 17, 2020	$0.01
Restricted shares without performance criteria	34,450	March 17, 2017	March 17, 2021	$0.01
Restricted shares with performance criteria	228,500	March 17, 2017	March 17, 2020	$0.01