PARENT COMPANY CONDENSED FINANCIAL STATEMENTS (Details 5) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 110,734	$ 110,143	$ 103,284	$ 107,516	$ 91,805	$ 94,097	$ 98,748	$ 100,027	$ 431,677	$ 384,677	$ 345,878
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									83,348	46,202	82,553
Net cash provided by operating activities									641,856	469,624	392,898
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in tax credit investments									(87,860)	(95,074)	(87,925)
Purchases of:
Available-for-sale investment securities									(2,396,199)	(3,547,193)	(960,135)
Proceeds from sale of:
Available-for-sale investment securities									1,275,645	1,669,334	623,689
Net cash used in investing activities									(1,792,660)	(3,627,881)	(2,359,893)
Proceeds from:
Issuance of common stock pursuant to various stock compensation plans and agreements									2,982	2,835	6,794
Payments for:
Repurchase of vested shares due to employee tax liability									(3,225)	(5,964)	(10,326)
Other net financing activities									1,055	3,291	6,513
Net cash provided by financing activities									1,680,360	3,490,306	2,111,060
NET INCREASE IN CASH AND CASH EQUIVALENTS									517,616	321,002	144,065
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR				1,360,887				1,039,885	1,360,887	1,039,885	895,820
CASH AND CASH EQUIVALENTS, END OF YEAR	1,878,503				1,360,887				1,878,503	1,360,887	1,039,885
Cash paid during the year for:
Interest									104,251	105,831	112,695
Noncash investing and financing activities:
Issuance of common stock related to acquisition											190,830
Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES
Net income									431,677	384,677	345,878
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed income of subsidiaries									(330,006)	(387,966)	(317,620)
Depreciation and amortization									14,094	22,870	46,365
Gains on sales of available-for-sale investment securities and other investments									0	(20)	(4,357)
Net change in other assets and other liabilities									47,072	(40,624)	179,869
Net cash provided by operating activities									162,837	(21,063)	250,135
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in tax credit investments									(6,554)	(35,633)	(53,071)
Purchases of:
Available-for-sale investment securities									0	0	(9,000)
Proceeds from sale of:
Available-for-sale investment securities									0	20	74,002
Net cash used in investing activities									(6,554)	(35,613)	11,931
Proceeds from:
Issuance of common stock pursuant to various stock compensation plans and agreements									2,081	2,835	6,794
Payments for:
Repayment of long-term debt									(20,000)	(20,000)	(30,310)
Repurchase of vested shares due to employee tax liability									(3,225)	(5,964)	(10,326)
Cash dividends on common stock									(115,828)	(115,641)	(103,618)
Other net financing activities									1,055	3,291	6,513
Net cash provided by financing activities									(135,917)	(135,479)	(130,947)
NET INCREASE IN CASH AND CASH EQUIVALENTS									20,366	(192,155)	131,119
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR				$ 18,898				$ 211,053	18,898	211,053	79,934
CASH AND CASH EQUIVALENTS, END OF YEAR	$ 39,264				$ 18,898				39,264	18,898	211,053
Cash paid during the year for:
Interest									4,691	4,254	4,462
Noncash investing and financing activities:
Issuance of common stock related to acquisition									$ 0	$ 0	$ 190,830