Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
NET EARNINGS	$ 104,774	$ 100,381	$ 89,559
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	11,573	11,145	9,262
PROVISION FOR LOAN LOSSES	10,212	9,685	4,465
Securities premium amortization (discount accretion), net	29,005	27,705	20,221
Gain on sale of assets, net	(1,894)	(150)	(910)
Deferred federal income tax expense (benefit)	673	320	(893)
Change in loans held for sale	6,645	(24,739)	(3,640)
Change in other assets	2,397	(16,919)	9,852
Change in other liabilities	(2,643)	1,664	3,486
Total adjustments	55,968	8,711	41,843
Net cash provided by operating activities	160,742	109,092	131,402
CASH FLOWS FROM INVESTING ACTIVITIES:
Cash paid for asset acquisition of 4Trust Mortgage, Inc., net		(1,931)
Cash received in acquisition of FBC Bancshares, Inc., net		65,197
Net decrease in interest-bearing time deposits in banks	1,788	13,507	14,915
Activity in available-for-sale securities:
Sales	40,510	35,580	1,619
Maturities	3,509,113	2,717,724	2,917,407
Purchases	(3,737,865)	(3,055,117)	(3,248,804)
Activity in held-to-maturity securities - maturities	157	163	243
Net increase in loans	(48,836)	(144,320)	(247,829)
Purchases of bank premises and equipment and other assets	(20,399)	(17,433)	(17,412)
Proceeds from sale of bank premises and equipment and other assets	3,572	2,405	4,656
Net cash used in (provided by) investing activities	(251,960)	(384,225)	(575,205)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in noninterest-bearing deposits	(28,230)	23,473	208,146
Net increase in interest-bearing deposits	316,600	72,857	407,035
Net increase (decrease) in borrowings	(169,905)	235,440	(96,778)
Common stock transactions:
Proceeds from stock issuances	1,260	1,545	1,437
Dividends paid	(44,907)	(38,767)	(34,578)
Net cash provided by financing activities	74,818	294,548	485,262
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(16,400)	19,415	41,459
CASH AND CASH EQUIVALENTS, beginning of year	272,886	253,471	212,012
CASH AND CASH EQUIVALENTS, end of year	$ 256,486	$ 272,886	$ 253,471