PARENT COMPANY CONDENSED FINANCIAL STATEMENTS (Details 3) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 91,805	$ 94,097	$ 98,748	$ 100,027	$ 95,502	$ 91,900	$ 84,305	$ 74,171	$ 384,677	[1]	$ 345,878	[1]	$ 293,324	[1]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									46,202		82,553		75,814
Tax benefit from stock compensation plans, net									(3,291)		(6,513)		(5,522)
Net cash provided by operating activities									469,624		392,898		425,845
Purchases of:
Available-for-sale investment securities									(3,547,193)		(960,135)		(1,316,764)
Proceeds from sale of:
Available-for-sale investment securities									1,669,334		623,689		663,569
Net cash used in investing activities									(3,627,881)		(2,359,893)		(2,734,846)
Proceeds from:
Issuance of common stock pursuant to various stock plans and agreements									2,835		6,794		3,054
Payments for:
Repayment of long-term debt									(20,000)		(30,310)		(10,310)
Repurchase of vested shares due to employee tax liability									(5,964)		(10,326)		(13,833)
Repurchase of shares of treasury stock pursuant to the Stock Repurchase Plan									0		0		(199,992)
Tax benefit from stock compensation plans, net									3,291		6,513		5,522
Net cash provided by financing activities									3,490,306		2,111,060		1,881,715
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS									321,002		144,065		(427,286)
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR				1,039,885				895,820	1,039,885		895,820		1,323,106
CASH AND CASH EQUIVALENTS, END OF YEAR	1,360,887				1,039,885				1,360,887		1,039,885		895,820
Cash paid during the year for:
Interest									105,831		112,695		112,169
Noncash investing and financing activities:
Conversion of preferred stock to common stock									0		0		83,027
Issuance of common stock related to acquisition											190,830
Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES
Net income									384,677		345,878		293,324
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed income of subsidiaries									(387,965)		(317,620)		(289,309)
Depreciation and amortization									22,870		46,365		8,806
Gains on sales of available-for-sale investment securities and other investments									(20)		(4,357)		(161)
Tax benefit from stock compensation plans, net									(3,291)		(6,513)		(5,522)
Net change in other assets and other liabilities									(37,334)		186,382		293,112
Net cash provided by operating activities									(21,063)		250,135		300,250
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in tax credit investments									(35,633)		(53,071)		(12,970)
Purchases of:
Available-for-sale investment securities									0		(9,000)		(69,986)
Proceeds from sale of:
Available-for-sale investment securities									20		74,002		0
Net cash used in investing activities									(35,613)		11,931		(82,956)
Proceeds from:
Increase in long-term borrowings									0		0		100,000
Issuance of common stock pursuant to various stock plans and agreements									2,835		6,794		3,054
Payments for:
Repayment of long-term debt									(20,000)		(30,310)		(10,310)
Repurchase of vested shares due to employee tax liability									(5,964)		(10,326)		(13,833)
Repurchase of shares of treasury stock pursuant to the Stock Repurchase Plan									0		0		(199,992)
Cash dividends on common stock									(115,641)		(103,618)		(82,862)
Cash dividends on preferred stock									0		0		(3,428)
Tax benefit from stock compensation plans, net									3,291		6,513		5,522
Net cash provided by financing activities									(135,479)		(130,947)		(201,849)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS									(192,155)		131,119		15,445
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR				$ 211,053				$ 79,934	211,053		79,934		64,489
CASH AND CASH EQUIVALENTS, END OF YEAR	$ 18,898				$ 211,053				18,898		211,053		79,934
Cash paid during the year for:
Interest									4,254		4,462		3,292
Noncash investing and financing activities:
Conversion of preferred stock to common stock									0		0		83,027
Issuance of common stock related to acquisition									$ 0		$ 190,830		$ 0

[1] Prior period was restated to reflect the retrospective application of adopting the new accounting guidance related to the Company’s investments in qualified affordable housing projects Accounting Standards Update (“ASU”) 2014-01. Please see Note 9 — Investments in Qualified Affordable Housing Partnerships, Tax Credit and Other Investments, Net to the Consolidated Financial Statements for additional information.