PARENT COMPANY CONDENSED FINANCIAL STATEMENTS (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 92,998	$ 88,756	$ 83,988	$ 76,741	$ 75,782	$ 73,157	$ 74,015	$ 72,091	$ 342,483	$ 295,045	$ 281,650
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									127,625	101,169	82,536
Stock compensation costs									13,883	13,548	12,668
Tax benefit from stock compensation plans, net									(6,513)	(5,522)	(462)
Net cash provided by operating activities									392,898	425,845	287,526
Purchases of:
Investment securities available-for-sale									(960,135)	(1,316,764)	(1,835,823)
Proceeds from sale of:
Investment securities available-for-sale									623,689	663,569	1,230,134
Net cash used in investing activities									(2,359,893)	(2,734,846)	(758,905)
Payment for:
Repayment of long-term debt									(30,310)	(10,310)	(75,000)
Repurchase of vested shares due to employee tax liability									(10,326)	(13,833)	(3,012)
Repurchase of shares of treasury stock pursuant to the Stock Repurchase Plan										(199,992)	(199,950)
Proceeds from:
Issuance of common stock pursuant to various stock plans and agreements									6,794	3,054	3,821
Tax benefit from stock compensation plans, net									6,513	5,522	462
Net cash provided by financing activities									2,111,060	1,881,715	364,200
NET INCREASE IN CASH AND CASH EQUIVALENTS									144,065	(427,286)	(108,079)
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR				895,820				1,323,106	895,820	1,323,106	1,431,185
CASH AND CASH EQUIVALENTS, END OF YEAR	1,039,885				895,820				1,039,885	895,820	1,323,106
Cash paid during the year for:
Interest									112,695	112,169	136,760
Noncash investing and financing activities:
Conversion of preferred stock to common stock										83,027
Issuance of common stock related to acquisition									190,830
Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES
Net income									342,483	295,045	281,650
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed (income) of subsidiaries									(314,225)	(291,659)	(285,636)
Depreciation and amortization									46,365	8,806	445
Gains on sales of investment securities and other investments									(4,357)	(161)
Tax benefit from stock compensation plans, net									(6,513)	(5,522)	(462)
Net change in other assets									186,232	293,153	322,361
Net change in other liabilities									150	(41)	(25)
Net cash provided by operating activities									250,135	299,621	318,333
Purchases of:
Investment securities available-for-sale									(9,000)	(69,986)
Equity investments									(53,071)	(12,970)	(234)
Proceeds from sale of:
Investment securities available-for-sale									74,002
Net cash used in investing activities									11,931	(82,956)	(234)
Payment for:
Repayment of long-term debt									(30,310)	(10,310)
Repurchase of vested shares due to employee tax liability									(10,326)	(13,833)	(3,012)
Cash dividends on preferred stock										(3,428)	(6,857)
Cash dividends on common stock									(103,618)	(82,862)	(57,361)
Repurchase of shares of treasury stock pursuant to the Stock Repurchase Plan										(199,992)	(199,950)
Proceeds from:
Increase in long-term borrowings										100,000
Issuance of common stock pursuant to various stock plans and agreements									6,794	3,683	3,821
Tax benefit from stock compensation plans, net									6,513	5,522	462
Net cash provided by financing activities									(130,947)	(201,220)	(262,897)
NET INCREASE IN CASH AND CASH EQUIVALENTS									131,119	15,445	55,202
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR				79,934				64,489	79,934	64,489	9,287
CASH AND CASH EQUIVALENTS, END OF YEAR	211,053				79,934				211,053	79,934	64,489
Cash paid during the year for:
Interest									4,462	3,292	3,112
Noncash investing and financing activities:
Conversion of preferred stock to common stock										83,027
Issuance of common stock related to acquisition									$ 190,830