Condensed Parent Company Financial Statements - Schedule of Condensed Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Cash and due from banks	$ 234,796	$ 169,186
Other assets	215,762	176,374
Total Assets	15,720,112	12,458,632
LIABILITIES
Junior subordinated debt owed to unconsolidated subsidiary trusts	138,222
Total Liabilities	13,126,191	10,479,805
SHAREHOLDERS’ EQUITY	2,593,921	1,978,827	$ 1,395,321	$ 1,341,408
Total Liabilities and Shareholders’ Equity	15,720,112	12,458,632
Parent Company [Member]
ASSETS
Cash and due from banks	170,854	121,857
Investment in subsidiaries—Bank	2,572,915	1,991,452
Investment in subsidiaries—Nonbank	9,170	12,322
Securities available-for-sale, at fair value	225	1,212
Other assets	38,393	33,159
Total Assets	2,791,557	2,160,002
LIABILITIES
Junior subordinated debt owed to unconsolidated subsidiary trusts	174,660	164,356
Dividends payable and other liabilities	22,976	16,819
Total Liabilities	197,636	181,175
SHAREHOLDERS’ EQUITY	2,593,921	1,978,827
Total Liabilities and Shareholders’ Equity	$ 2,791,557	$ 2,160,002