Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
NET EARNINGS	$ 112,202	$ 84,227
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	9,554	9,447
PROVISION FOR LOAN LOSSES	3,865	5,090
Securities premium amortization (discount accretion), net	21,005	23,009
Gain on sale of assets, net	(1,254)	(1,572)
Deferred federal income tax benefit	8,107	1,290
Change in loans held-for-sale	(2,928)	7,779
Change in other assets	2,699	18,703
Change in other liabilities	5,653	7,172
Total adjustments	46,701	70,918
Net cash provided by operating activities	158,903	155,145
CASH FLOWS FROM INVESTING ACTIVITIES:
Cash received in acquisition of Commercial Bancshares, Inc.	18,653
Net decrease in interest-bearing time deposits in banks		249
Activity in available-for-sale securities:
Sales	220,259	120,576
Maturities	3,354,571	4,299,781
Purchases	(3,650,127)	(4,450,719)
Activity in held-to-maturity securities - maturities		124
Net increase in loans	(116,860)	(119,911)
Purchases of bank premises and equipment and other assets	(12,381)	(12,626)
Proceeds from sale of bank premises and equipment and other assets	810	4,857
Net cash used in investing activities	(185,075)	(157,669)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in noninterest-bearing deposits	(56,706)	231,452
Net increase in interest-bearing deposits	(102,875)	(12,531)
Net increase (decrease) in borrowings	49,760	(94,335)
Common stock transactions:
Proceeds from stock issuances	2,800	2,260
Dividends paid	(39,645)	(36,373)
Net cash provided by (used in) financing activities	(146,666)	90,473
NET DECREASE IN CASH AND CASH EQUIVALENTS	(172,838)	87,949
CASH AND CASH EQUIVALENTS, beginning of period	372,347	256,486
CASH AND CASH EQUIVALENTS, end of period	199,509	344,435
SUPPLEMENTAL INFORMATION AND NONCASH TRANSACTIONS:
Interest paid	12,617	6,772
Federal income taxes paid	20,351	21,896
Transfer of loans and bank premises to other real estate	126	2,044
Investment securities purchased but not settled	13,453	993
Restricted stocks grant to directors and officers	523	$ 600
Stock issued in acquisition of Commercial Bancshares, Inc.	$ 58,087