CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands		Common Stock	Additional Paid In Capital Common Stock	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive (Loss) Income, Net of Tax	Total
BALANCE at Dec. 31, 2013	[1]	$ 163	$ 1,571,670	$ 1,362,278	$ (537,279)	$ (30,459)	$ 2,366,373
Increase (Decrease) in Stockholders' Equity
Net income	[1]			158,476			158,476
Other comprehensive income						27,924	27,924
Stock compensation costs			6,745				6,745
Tax benefit from stock compensation plans, net			3,787				3,787
Issuance of 409,885 and 390,195 shares of common stock pursuant to various stock compensation plans and agreements for the period ended June 30, 2015 and 2014, respectively			1,207				1,207
Cancellation of 12,959 shares of common stock due to forfeitures of issued restricted stock for the period ended June 30, 2014			241		(241)
143,078 and 202,070 shares of restricted stock surrendered due to employee tax liability for the period ended June 30, 2015 and 2014, respectively					(7,308)		(7,308)
Common stock dividends				(51,970)			(51,970)
Issuance of 5,583,093 shares pursuant to MetroCorp Bancshares, Inc. acquisition			73,044		117,786		190,830
Warrant acquired pursuant to MetroCorp Bancshares, Inc. acquisition			4,855				4,855
BALANCE at Jun. 30, 2014	[1]	163	1,661,549	1,468,784	(427,042)	(2,535)	2,700,919
BALANCE at Dec. 31, 2014	[1]	164	1,677,767	1,604,141	(430,198)	4,237	2,856,111
Increase (Decrease) in Stockholders' Equity
Net income				198,775			198,775
Other comprehensive income						1,193	1,193
Stock compensation costs			7,652				7,652
Tax benefit from stock compensation plans, net			3,196				3,196
Issuance of 409,885 and 390,195 shares of common stock pursuant to various stock compensation plans and agreements for the period ended June 30, 2015 and 2014, respectively			1,769				1,769
143,078 and 202,070 shares of restricted stock surrendered due to employee tax liability for the period ended June 30, 2015 and 2014, respectively					(5,787)		(5,787)
Common stock dividends				(57,961)			(57,961)
BALANCE at Jun. 30, 2015		$ 164	$ 1,690,384	$ 1,744,955	$ (435,985)	$ 5,430	$ 3,004,948

[1] Prior periods were 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. See Note 10 of the Notes to Consolidated Financial Statements for additional information.