CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Additional Paid In Capital Preferred Stock	Common Stock	Additional Paid In Capital Common Stock	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss), Net of Tax
BALANCE at Dec. 31, 2012	$ 2,382,122	$ 83,027	$ 157	$ 1,464,739	$ 1,151,828	$ (322,298)	$ 4,669
Increase (Decrease) in Stockholders' Equity
Net income	72,091				72,091
Other comprehensive income	1,516						1,516
Stock compensation costs	2,504			2,504
Tax benefit from stock compensation plans, net	2,602			2,602
Issuance of 356,187 and 193,831 shares of common stock pursuant to various stock compensation plans and agreements for the period ended March 31, 2014 and 2013, respectively	442			442
Cancellation of 7,233 and 22,050 shares of common stock due to forfeitures of issued restricted stock for the period ended March 31, 2014 and 2013, respectively				387		(387)
195,291 and 344,423 shares of restricted stock surrendered due to employee tax liability for the period ended March 31, 2014 and 2013, respectively	(8,365)					(8,365)
Preferred stock dividends	(1,714)				(1,714)
Common stock dividends	(21,079)				(21,079)
Purchase of 3,543,100 shares of treasury stock pursuant to the Stock Repurchase Program	(87,000)					(87,000)
BALANCE at Mar. 31, 2013	2,343,119	83,027	157	1,470,674	1,201,126	(418,050)	6,185
BALANCE at Dec. 31, 2013	2,364,225		163	1,571,670	1,360,130	(537,279)	(30,459)
Increase (Decrease) in Stockholders' Equity
Net income	76,741				76,741
Other comprehensive income	13,422						13,422
Stock compensation costs	3,180			3,180
Tax benefit from stock compensation plans, net	3,708			3,708
Issuance of 356,187 and 193,831 shares of common stock pursuant to various stock compensation plans and agreements for the period ended March 31, 2014 and 2013, respectively	283			283
Cancellation of 7,233 and 22,050 shares of common stock due to forfeitures of issued restricted stock for the period ended March 31, 2014 and 2013, respectively				127		(127)
195,291 and 344,423 shares of restricted stock surrendered due to employee tax liability for the period ended March 31, 2014 and 2013, respectively	(7,074)					(7,074)
Common stock dividends	(25,950)				(25,950)
Issuance of 5,583,093 shares pursuant to MetroCorp acquisition	190,830			73,044		117,786
Warrant acquired pursuant to MetroCorp acquisition	4,855			4,855
BALANCE at Mar. 31, 2014	$ 2,624,220		$ 163	$ 1,656,867	$ 1,410,921	$ (426,694)	$ (17,037)