Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Statement of Cash Flows [Abstract]
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 98,498	$ 35,919
INVESTING ACTIVITIES
Proceeds from maturities and calls of securities held to maturity	2	12,888
Proceeds from sales of securities available for sale	53,179	234,816
Proceeds from maturities and calls of securities available for sale	124,894	332,488
Purchases of securities available for sale	(391,186)	(524,561)
Proceeds from sales of equity securities	1,826	0
Purchases of equity securities	(380)	0
Proceeds from sales and redemptions of other investment securities	15,606	9,272
Purchases of other investment securities	(33,279)	(43,337)
Purchases of bank premises and equipment	(2,159)	(2,798)
Proceeds from sales of bank premises and equipment	2,123	13
Proceeds from the sales of OREO properties	4,658	3,835
Acquisition of subsidiaries, net of cash paid	0	44,531
Net change in loans	(493,787)	112,150
NET CASH (USED IN) PROVIDED BY INVESTING ACTIVITIES	(718,503)	179,297
FINANCING ACTIVITIES
Cash dividends paid	(71,461)	(52,092)
Acquisition of treasury stock	(35,984)	(1)
Proceeds from exercise of stock options	851	2,546
Repayment of long-term Federal Home Loan Bank borrowings	(625,000)	(825,191)
Proceeds from issuance of long-term Federal Home Loan Bank borrowings	1,115,000	845,000
Repayment of trust preferred issuance	(9,374)	0
Changes in:
Deposits	812	(174,557)
Federal funds purchased, securities sold under agreements to repurchase and other short-term borrowings	(328,080)	(34,444)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	46,764	(238,739)
Decrease in cash and cash equivalents	(573,241)	(23,523)
Cash and cash equivalents at beginning of year	1,666,167	1,434,527
Cash and cash equivalents at end of period	1,092,926	1,411,004
Noncash investing activities:
Transfers of loans to OREO	$ 527	$ 1,951