Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest income
Interest and fees on loans	$ 675,875	$ 573,128	$ 383,545
Interest on investment securities:
Taxable	62,231	31,496	10,989
Tax-exempt	24,286	18,343	12,317
Dividends on nonmarketable equity securities	7,877	4,924	1,973
Interest on deposits with the Federal Reserve Bank, other banks and Federal funds sold	5,727	4,244	1,555
Total interest income	775,996	632,135	410,379
Interest expense
Interest on deposits	96,980	46,727	23,021
Interest on collateralized customer deposits	2,607	1,269	303
Interest on short-term borrowings	37,510	19,052	1,357
Interest on long-term borrowings	6,566	7,509	4,617
Total interest expense	143,663	74,557	29,298
Net interest income	632,333	557,578	381,081
Provision for loan losses	30,750	23,300	14,875
Net interest income after provision for loan losses	601,583	534,278	366,206
Noninterest income
Net gain on sale of loans and other mortgage banking revenue	35,193	32,205	21,859
Net gain (loss) on sale of investment securities	224	(7,388)	129
Gain on sale of branch offices	0	0	7,391
Other	28,589	25,918	11,988
Total noninterest income	148,536	144,019	122,350
Operating expenses
Salaries, wages and employee benefits	225,427	215,562	165,862
Occupancy	31,670	30,554	23,525
Equipment and software	31,761	32,248	24,408
Outside processing and service fees	45,387	35,142	21,199
Merger expenses	0	8,522	61,134
Restructuring expenses	0	19,880	0
Other	89,953	80,086	42,290
Total operating expenses	424,198	421,994	338,418
Income before income taxes	325,921	256,303	150,138
Income tax expense	41,901	106,780	42,106
Net income	$ 284,020	$ 149,523	$ 108,032
Earnings per common share:
Basic (in dollars per share)	$ 3.98	$ 2.11	$ 2.21
Diluted (in dollars per share)	$ 3.94	$ 2.08	$ 2.17
Service charges and fees on deposit accounts
Noninterest income
Noninterest income	$ 37,097	$ 38,367	$ 30,724
Wealth management revenue
Noninterest income
Noninterest income	25,996	25,512	22,601
Other charges and fees for customer services
Noninterest income
Noninterest income	$ 21,437	$ 29,405	$ 27,658