Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
NET EARNINGS	$ 84,227	$ 78,108
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	9,447	8,627
PROVISION FOR LOAN LOSSES	5,090	8,219
Securities premium amortization (discount accretion), net	23,009	21,275
Gain on sale of assets, net	(1,572)	(1,767)
Deferred federal income tax benefit	1,290	825
Change in loans held-for-sale	7,779	1,952
Change in other assets	18,703	10,059
Change in other liabilities	7,172	530
Total adjustments	70,918	49,720
Net cash provided by operating activities	155,145	127,828
CASH FLOWS FROM INVESTING ACTIVITIES:
Net decrease in interest-bearing time deposits in banks	249	1,788
Activity in available-for-sale securities:
Sales	120,576	20,792
Maturities	4,299,781	2,830,522
Purchases	(4,450,719)	(2,835,964)
Activity in held-to-maturity securities - maturities	124	148
Net increase in loans	(119,911)	(27,446)
Purchases of bank premises and equipment and other assets	(12,626)	(17,151)
Proceeds from sale of other assets	4,857	2,960
Net cash used in investing activities	(157,669)	(24,351)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in noninterest-bearing deposits	231,452	(42,959)
Net increase (decrease) in interest-bearing deposits	(12,531)	88,254
Net decrease in borrowings	(94,335)	(101,916)
Common stock transactions:
Proceeds from stock issuances	2,260	989
Dividends paid	(36,373)	(33,016)
Net cash provided by (used in) financing activities	90,473	(88,648)
NET DECREASE IN CASH AND CASH EQUIVALENTS	87,949	14,829
CASH AND CASH EQUIVALENTS, beginning of period	256,486	272,886
CASH AND CASH EQUIVALENTS, end of period	344,435	287,715
SUPPLEMENTAL INFORMATION AND NONCASH TRANSACTIONS:
Interest paid	6,772	4,018
Federal income tax paid	21,896	21,631
Transfer of loans and bank premises to other real estate owned	2,044	1,905
Investment securities purchased but not settled	993	4,521
Restricted stock grant to officers and directors	$ 600	$ 250