Net income per common share - Computation of net income (loss) per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Earnings Per Share
Net income	$ 1,102,641	$ 934,889	$ 506,622
Preferred stock dividends	(1,412)	(1,412)	(1,758)
Net income applicable to common stock	$ 1,101,229	$ 933,477	$ 504,864
Average common shares outstanding	75,147,263	81,263,027	85,882,371
Average potential dilutive common shares	126,740	157,127	92,888
Average common shares outstanding - assuming dilution	75,274,003	81,420,154	85,975,259
Basic EPS	$ 14.65	$ 11.49	$ 5.88
Diluted EPS	$ 14.63	$ 11.46	$ 5.87