Parent company only financial statements - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 232,681	$ 125,356
Other assets	122,714	70,102
Goodwill	169,051	137,190	$ 137,190
Total assets	6,124,921	5,136,764	4,727,713
LIABILITIES
Accrued expenses and other liabilities	87,454	65,414
Total liabilities	5,362,592	4,464,907
SHAREHOLDERS' EQUITY
Common stock	31,034	30,725
Additional paid-in capital	425,633	424,146
Retained earnings	293,524	221,213
Accumulated other comprehensive (loss) income	12,138	(4,227)
Total shareholders' equity	762,329	671,857	596,729	$ 330,498
Total liabilities and shareholders' equity	6,124,921	5,136,764
Parent Company
ASSETS
Cash and cash equivalents	4,673	17,400	$ 25,789	$ 30,993
Investments in Bank subsidiary	782,565	679,097
Other assets	6,292	7,364
Goodwill	29	29
Total assets	793,559	703,890
LIABILITIES
Borrowings	30,930	30,930
Accrued expenses and other liabilities	300	1,103
Total liabilities	31,230	32,033
SHAREHOLDERS' EQUITY
Common stock	31,034	30,725
Additional paid-in capital	425,633	424,146
Retained earnings	293,524	221,213
Accumulated other comprehensive (loss) income	12,138	(4,227)
Total shareholders' equity	762,329	671,857
Total liabilities and shareholders' equity	$ 793,559	$ 703,890