Net income per common share - Computation of net income (loss) per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share, Basic and Diluted [Abstract]
Net income	$ 422,395	$ 248,114	$ 845,502	$ 728,825
Preferred stock dividends	(353)	(353)	(1,059)	(1,059)
Net income applicable to common stock	$ 422,042	$ 247,761	$ 844,443	$ 727,766
Average common shares outstanding	73,955,184	80,126,166	76,173,783	81,864,634
Average potential dilutive common shares	102,148	148,776	130,436	149,479
Average common shares outstanding - assuming dilution	74,057,332	80,274,942	76,304,219	82,014,113
Basic EPS	$ 5.71	$ 3.09	$ 11.09	$ 8.89
Diluted EPS	$ 5.70	$ 3.09	$ 11.07	$ 8.87