Segment Information - Results of Operations and Selected Financial Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net interest income	$ 74,073	$ 66,903
Noninterest income	35,145	32,001
Income before taxes	28,250	41,014
Total Assets	8,669,096		$ 8,565,758
Operating Segments [Member] | Metropolitan Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	22,184	21,353
Noninterest income	4,700	4,209
Income before taxes	10,413	15,369
Total Assets	2,863,800		2,806,021
Operating Segments [Member] | Community Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	44,498	43,407
Noninterest income	15,853	14,885
Income before taxes	24,436	28,045
Total Assets	5,157,675		4,998,247
Operating Segments [Member] | Pegasus Bank [Member]
Segment Reporting Information [Line Items]
Net interest income	5,608
Noninterest income	131
Income before taxes	1,598
Total Assets	757,946		738,351
Operating Segments [Member] | Other Financial Services [Member]
Segment Reporting Information [Line Items]
Net interest income	1,583	1,171
Noninterest income	10,890	9,873
Income before taxes	5,759	4,499
Total Assets	108,546		102,442
Operating Segments [Member] | Executive, Operations & Support [Member]
Segment Reporting Information [Line Items]
Net interest income	200	972
Noninterest income	27,483	35,521
Income before taxes	9,403	25,023
Total Assets	845,160		950,920
Eliminations [Member]
Segment Reporting Information [Line Items]
Noninterest income	(23,912)	(32,487)
Income before taxes	(23,359)	$ (31,922)
Total Assets	$ (1,064,031)		$ (1,030,223)