Condensed Financial Information (parent company only) - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Premises and equipment	$ 113,055	$ 93,420
Interest receivable	48,901	40,881
Goodwill	543,918	445,355	$ 445,355
Cash surrender value of life insurance	288,206	224,939
Other assets	100,194	47,772
TOTAL ASSETS	12,457,254	9,884,716
Liabilities
Subordinated debentures and term loans	138,685	138,463
Interest payable	6,754	5,607
Other liabilities	91,404	45,295
Total Liabilities	10,670,817	8,476,456
Stockholders' equity	1,786,437	1,408,260	$ 1,303,463	$ 901,657
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	12,457,254	9,884,716
Parent
Assets
Cash	127,723	87,435
Investment in subsidiaries	1,791,070	1,459,036
Premises and equipment	153	1,158
Interest receivable	6	6
Goodwill	448	448
Cash surrender value of life insurance	837	810
Other assets	16,803	5,240
TOTAL ASSETS	1,937,040	1,554,133
Liabilities
Subordinated debentures and term loans	138,685	138,463
Interest payable	977	994
Other liabilities	10,941	6,416
Total Liabilities	150,603	145,873
Stockholders' equity	1,786,437	1,408,260
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 1,937,040	$ 1,554,133