Earnings per share attributable to stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Net income attributable to:
Basic	$ 28,188	$ 22,809
Diluted	$ 28,188	$ 22,809
Weighted average number of shares outstanding:
Basic	109,972,997	109,248,880
Diluted	111,267,392	110,482,837
Per Share Amount
Basic	$ 0.26	$ 0.21
Diluted	$ 0.25	$ 0.21
Share Units [Member]
Weighted average number of shares outstanding:
Effect of dilutive securities:	579,133	586,074
Stock Options [Member]
Weighted average number of shares outstanding:
Effect of dilutive securities:	715,262	647,883
Per Share Amount
Effect of dilutive securities:	(0.01)