Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net earnings	$ 357,818	$ 352,166	$ 299,619
Depreciation and amortization	32,029	32,884	24,885
Accretion (Amortization) of Discounts and Premiums, Investments	41,450	39,797	19,675
Intangible asset amortization	14,240	16,517	9,410
Provision for credit losses	57,752	65,729	45,481
Gain on sale of foreclosed assets, net	(871)	(837)	(2,967)
Provision for losses on foreclosed assets	2,138	2,576	5,228
Gain on sale of loans and leases, net	(6,197)	(909)	(373)
(Gain) loss on sale of premises and equipment	(386)	78	(28)
Loss (gain) on sale of securities, net	541	(9,485)	(3,744)
Gain (Loss) on Sale of Insurance Block	(1,050)	(539)	0
Unrealized gain on derivatives and foreign currencies, net	(429)	(202)	(160)
Earned stock compensation	25,568	23,319	15,630
Gain (Loss) on Sale of Capital Leases, Net	0	720	0
Decrease in deferred income taxes, net	76,860	53,556	149,664
Tax effect included in stockholders' equity of restricted stock vesting	0	(4,406)	(841)
(Increase) decrease in other assets	(118,477)	6,441	48,172
Increase (decrease) in accrued interest payable and other liabilities	2,982	3,702	(15,773)
Net cash provided by operating activities	483,968	581,107	593,878
Cash flows from investing activities:
Cash acquired in acquisitions, net of cash consideration paid	160,318	0	260,936
Proceeds (Net Cash Used) From Branch Sale	0	(178,792)	0
Net increase in loans and leases	(1,303,752)	(1,257,734)	(1,105,925)
Proceeds from sales of loans and leases	1,322,456	121,053	31,993
Proceeds from maturities and paydowns of securities available-for-sale	435,925	250,170	144,847
Proceeds from sales of securities available-for-sale	759,300	393,509	1,035,926
Purchases of securities available-for-sale	(1,298,105)	(375,261)	(992,680)
Net redemptions (purchases) of Federal Home Loan Bank stock	12,982	(2,160)	23,686
Proceeds from sales of foreclosed assets	12,345	8,186	32,812
Purchases of premises and equipment, net	(7,919)	(8,183)	(8,929)
Proceeds from sales of premises and equipment	10,309	24	146
Proceeds from Sale and Collection of Lease Receivables	0	138,955	0
Proceeds from Life Insurance Policy	2,478	3,238	0
Net increase in equipment leased to others under operating leases	(73,596)	(51,557)	(65,309)
Net cash provided by (used in) investing activities	32,741	(958,552)	(642,497)
Cash flows from financing activities:
Net increase in noninterest-bearing deposits	343,663	490,997	685,742
Net decrease in interest-bearing deposits	(63,700)	(104,021)	(569,706)
Net (decrease) increase in borrowings	(461,349)	285,928	238,512
Common stock repurchased and restricted stock surrendered	(109,153)	(33,244)	(8,400)
Tax effect of restricted stock vesting included in stockholders' equity	0	4,406	841
Cash dividends paid, net	(247,403)	(243,437)	(215,110)
Net cash (used in) provided by financing activities	(537,942)	400,629	131,879
Net (decrease) increase in cash and cash equivalents	(21,233)	23,184	83,260
Cash and cash equivalents, beginning of year	419,670	396,486	313,226
Cash and cash equivalents, end of year	398,437	419,670	396,486
Supplemental disclosures of cash flow information:
Cash paid for interest	69,477	54,389	65,868
Cash paid for income taxes	208,066	133,897	16,602
Real Estate Owned, Transfer to Real Estate Owned	580	781
Loans transferred to foreclosed assets		781	13,472
Transfer of Portfolio Loans and Leases to Held-for-sale	481,100	0	0
Partnership interest transferred to equipment leased to others under operating leases	0	0	20,833
Common stock issued in acquisitions	$ 446,233	$ 0	$ 797,433