Segment Information - Results of Operations and Selected Financial Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net interest income	$ 72,287	$ 65,673	$ 207,982	$ 193,588
Noninterest income	35,627	32,801	101,705	93,348
Income before taxes	42,965	41,918	127,807	118,695
Total Assets	8,388,816		8,388,816		$ 7,574,258
Operating Segments [Member] \| Metropolitan Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	21,955	21,313	64,746	62,701
Noninterest income	4,862	4,266	13,706	12,391
Income before taxes	15,670	16,538	45,905	46,157
Total Assets	2,720,095		2,720,095		2,743,876
Operating Segments [Member] \| Community Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	44,707	42,773	132,889	126,223
Noninterest income	16,823	15,404	47,951	44,189
Income before taxes	29,710	27,515	87,796	81,805
Total Assets	4,970,497		4,970,497		4,892,946
Operating Segments [Member] \| Pegasus Bank [Member]
Segment Reporting Information [Line Items]
Net interest income	2,954		2,954
Noninterest income	109		109
Income before taxes	1,404		1,404
Total Assets	731,400		731,400
Operating Segments [Member] \| Other Financial Services [Member]
Segment Reporting Information [Line Items]
Net interest income	1,654	1,241	4,236	4,074
Noninterest income	10,916	10,264	30,894	28,784
Income before taxes	6,239	4,440	16,310	13,511
Total Assets	112,527		112,527		84,706
Operating Segments [Member] \| Executive, Operations & Support [Member]
Segment Reporting Information [Line Items]
Net interest income	1,017	346	3,157	590
Noninterest income	39,640	36,503	113,078	102,306
Income before taxes	25,882	26,344	78,495	69,881
Total Assets	867,134		867,134		861,782
Eliminations [Member]
Segment Reporting Information [Line Items]
Noninterest income	(36,723)	(33,636)	(104,033)	(94,322)
Income before taxes	(35,940)	$ (32,919)	(102,103)	$ (92,659)
Total Assets	$ (1,012,837)		$ (1,012,837)		$ (1,009,052)

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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