Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income
Interest and fees on loans	$ 573,128	$ 383,545	$ 271,772
Interest on investment securities:
Taxable	31,496	10,989	8,786
Tax-exempt	18,343	12,317	9,073
Dividends on nonmarketable equity securities	4,924	1,973	1,648
Interest on deposits with the Federal Reserve Bank, other banks and Federal funds sold	4,244	1,555	510
Total interest income	632,135	410,379	291,789
Interest expense
Interest on deposits	46,727	23,021	15,406
Interest on short-term borrowings	20,321	1,660	453
Interest on long-term borrowings	7,509	4,617	1,922
Total interest expense	74,557	29,298	17,781
Net interest income	557,578	381,081	274,008
Provision for loan losses	23,300	14,875	6,500
Net interest income after provision for loan losses	534,278	366,206	267,508
Noninterest income
Service charges and fees on deposit accounts	35,001	28,136	25,481
Wealth management revenue	25,512	22,601	20,552
Other charges and fees for customer services	32,771	30,246	25,513
Net gain on sale of loans and other mortgage banking revenue	32,205	21,859	6,133
Net (loss) gain on sale of investment securities	(7,388)	129	630
Gain on sale of branch offices	0	7,391	0
Other	25,918	11,988	1,907
Total noninterest income	144,019	122,350	80,216
Operating expenses
Salaries, wages and employee benefits	213,828	165,213	127,920
Occupancy	30,554	23,525	18,213
Equipment and software	32,248	24,408	18,569
Outside processing and service fees	35,142	21,199	15,207
Merger expenses	8,522	61,134	7,804
Restructuring expenses	19,880	0	0
Other	81,820	42,939	36,181
Total operating expenses	421,994	338,418	223,894
Income before income taxes	256,303	150,138	123,830
Income tax expense	106,780	42,106	37,000
Net income	$ 149,523	$ 108,032	$ 86,830
Earnings per common share:
Basic (in dollars per share)	$ 2.11	$ 2.21	$ 2.41
Diluted (in dollars per share)	2.08	2.17	2.39
Cash dividends declared per common share (in dollars per share)	$ 1.10	$ 1.06	$ 1.0