Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 72,475	$ 49,014
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	6,551	6,915
Provision for loan losses	12,253	15,991
(Gain) loss on other real estate owned	210	(54)
Deferred tax expense	14,790	7,156
Increase in cash surrender value of life insurance contracts	(3,346)	(3,636)
Loss on disposal of other assets	73	229
Loss on sale of business	1,145
Net decrease in loans held for sale	18,172	13,966
Net amortization of securities premium/discount	8,453	7,323
Amortization of intangible assets	5,618	4,705
Amortization of FDIC indemnification assets		1,100
Stock-based compensation expense	4,883	4,209
Decrease in interest payable and other liabilities	(32,568)	(33,323)
Net payments to FDIC for loss share claims		(1,131)
Decrease in FDIC loss share receivable		902
Decrease in payable to FDIC for loan servicing	(11,107)
Decrease in other assets	6,821	21,362
Other, net	71	1,600
Net cash provided by operating activities	104,494	96,328
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities of securities available for sale	80,155	81,116
Purchases of securities available for sale	(142,052)	(60,484)
Proceeds from maturities of securities held to maturity	93,408	92,684
Purchases of securities held to maturity	(134,020)	(87,847)
Net decrease in short-term investments	30,843	9,428
Proceeds from sale of loans	12,211	33,279
Net increase in loans	(196,328)	(306,745)
Purchases of property and equipment	(7,904)	(7,329)
Proceeds from sales of property and equipment	42	17
Proceeds from sales of other real estate	1,641	3,099
Cash paid for acquisition, net of cash received		(322,708)
Proceeds from the sale of business, net of cash sold	77,081
Other, net	(8,915)	(39,588)
Net cash used in investing activities	(193,838)	(605,078)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in deposits	232,638	99,583
Net increase (decrease) in short-term borrowings	(251,793)	385,777
Repayments of long-term debt	(5,268)	(4,475)
Net proceeds from issuance of long-term debt	83	41
Dividends paid	(20,881)	(20,793)
Payroll tax remitted on net share settlement of equity awards	(142)	(163)
Proceeds from exercise of stock options	782	8,650
Proceeds from dividend reinvestment and stock purchase plans	837	755
Net cash provided by (used in) financing activities	(43,744)	469,375
NET DECREASE IN CASH AND DUE FROM BANKS	(133,088)	(39,375)
CASH AND DUE FROM BANKS, BEGINNING	386,948	372,689
CASH AND DUE FROM BANKS, ENDING	253,860	333,314
SUPPLEMENTAL INFORMATION FOR NON-CASH INVESTING AND FINANCING ACTIVITIES
Assets acquired in settlement of loans	$ 1,305	$ 1,031