Segment reporting - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) channel segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of distinct reportable segments | segment	2
Number of distinct delivery channels | channel	2
Total net contribution reclassification to (from) segment realignment	$ 243,051	$ 82,461	$ 109,539
Other noninterest expense	359,678	364,226	235,326
Relief of goodwill	0	0	100
Banking
Segment Reporting Information [Line Items]
Total net contribution reclassification to (from) segment realignment	216,598	(20,497)	99,859
Other noninterest expense	220,283	212,890	144,734
Mortgage
Segment Reporting Information [Line Items]
Total net contribution reclassification to (from) segment realignment	26,453	102,958	9,680
Interest paid	23,910	14,810	11,183
Other noninterest expense	$ 139,395	151,336	90,592
Relief of goodwill			100
Mortgage | Atlantic Capital
Segment Reporting Information [Line Items]
Other noninterest expense			1,995
Segment Realignment, Reclassification Adjustment | Banking
Segment Reporting Information [Line Items]
Total net contribution reclassification to (from) segment realignment		(26,416)	(7,213)
Segment Realignment, Reclassification Adjustment | Mortgage
Segment Reporting Information [Line Items]
Total net contribution reclassification to (from) segment realignment		$ 26,416	$ 7,213