Dividends on common stock: (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended
	May 27, 2022	Apr. 29, 2022	Mar. 31, 2022	Mar. 31, 2021
Dividends on common stock and return of capital program
Dividends paid			$ 41,298	$ 36,081
Subsequent Event
Dividends on common stock and return of capital program
Quarterly dividend payment approved (per share)		$ 0.88
Estimated
Dividends on common stock and return of capital program
Dividends paid	$ 41,000