Condensed Consolidated Statements of Earnings and Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest income:
Loans and leases, including fees	$ 79,818	$ 55,998	$ 192,382	$ 158,253
Investment securities:
Investment securities available-for-sale	11,521	12,240	35,086	37,887
Investment securities held-to-maturity	4,666	5,184	14,238	16,014
Total investment income	16,187	17,424	49,324	53,901
Dividends from FHLB stock	329	318	959	1,070
Interest-earning deposits with other institutions and federal funds sold	304	130	1,475	683
Total interest income	96,638	73,870	244,140	213,907
Interest expense:
Deposits	2,967	1,555	6,041	4,547
Borrowings and customer repurchase agreements	606	402	1,396	1,213
Junior subordinated debentures	245	174	674	492
Total interest expense	3,818	2,131	8,111	6,252
Net interest income before (recapture of) provision for loan losses	92,820	71,739	236,029	207,655
(Recapture of) provision for loan losses	500	(1,500)	(1,500)	(7,000)
Net interest income after (recapture of) provision for loan losses	92,320	73,239	237,529	214,655
Noninterest income:
BOLI income	936	692	2,984	2,904
Gain on OREO, net		2	3,540	4
Other	1,824	1,809	4,393	4,839
Total noninterest income	10,112	10,038	32,723	29,536
Noninterest expense:
Salaries and employee benefits	26,319	21,835	69,684	65,116
Occupancy and equipment	5,324	4,400	13,834	12,638
Professional services	1,154	1,091	4,374	4,191
Software licenses and maintenance	2,317	1,510	5,836	4,698
Marketing and promotion	1,134	1,055	3,638	3,484
Amortization of intangible assets	1,736	343	2,395	991
Acquisition related expenses	6,645	250	7,942	2,176
Other	4,251	4,222	11,377	12,402
Total noninterest expense	48,880	34,706	119,080	105,696
Earnings before income taxes	53,552	48,571	151,172	138,495
Income taxes	14,994	18,888	42,328	51,935
Net earnings	38,558	29,683	108,844	86,560
Other comprehensive income (loss):
Unrealized (loss) gain on securities arising during the period, before tax	(10,387)	1,221	(49,155)	3,287
Less: Reclassification adjustment for net gain on securities included in net income	0	0	0	(402)
Other comprehensive (loss) income, before tax	(10,387)	1,221	(49,155)	2,885
Less: Income tax benefit (expense) related to items of other comprehensive income	3,070	(513)	14,532	(1,212)
Other comprehensive (loss) income, net of tax	(7,317)	708	(34,623)	1,673
Comprehensive income	$ 31,241	$ 30,391	$ 74,221	$ 88,233
Basic earnings per common share	$ 0.30	$ 0.27	$ 0.94	$ 0.79
Diluted earnings per common share	$ 0.30	$ 0.27	$ 0.94	$ 0.79
Service Charges on Deposit Accounts [Member]
Noninterest income:
Revenue from contract with customer, including assessed tax	$ 4,295	$ 4,085	$ 12,431	$ 11,794
Trust and Investment Services [Member]
Noninterest income:
Revenue from contract with customer, including assessed tax	2,182	2,523	6,738	7,432
Bankcard Services [Member]
Noninterest income:
Revenue from contract with customer, including assessed tax	$ 875	$ 927	$ 2,637	$ 2,563