Stock option and award plan: Incentive award plan, additional information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Incentive Award Plan, additional information
Equity-based compensation expense	$ 26,822	$ 23,525	$ 18,460
Total unrecognized compensation cost	$ 39,400
Weighted-average period to recognize unrecognized compensation cost	2 years
Restricted stock
Incentive Award Plan, additional information
Granted (in dollars per share)	$ 64.59	$ 75.18	$ 53.53
Granted (in shares)	471,080	500,000	500,000
Equity-based compensation expense	$ 26,822	$ 23,525	$ 18,460
Income tax benefit related to stock options and restricted stock	6,314	4,211	3,026
Capitalized compensation expense related to stock options and restricted stock	3,222	2,275	1,752
Intrinsic value of stock options exercised	881	841	839
Fair value of shares of restricted stock vested	$ 35,749	$ 25,439	$ 20,779

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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