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, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share
Net income	$ 136,609	$ 422,395	$ 446,748	$ 845,502
Preferred stock dividends	(353)	(353)	(1,059)	(1,059)
Net income applicable to common stock	$ 136,256	$ 422,042	$ 445,689	$ 844,443
Average common shares outstanding	71,794,934	73,955,184	71,676,630	76,173,783
Average potential dilutive common shares	23,168	102,148	59,884	130,436
Average common shares outstanding - assuming dilution	71,818,102	74,057,332	71,736,514	76,304,219
Basic EPS	$ 1.90	$ 5.71	$ 6.22	$ 11.09
Diluted EPS	$ 1.90	$ 5.70	$ 6.21	$ 11.07