CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Common Stock and Additional Paid-In Capital	Retained Earnings	Treasury Stock	AOCI, net of tax
BALANCE (in shares) at Dec. 31, 2013		137,630,896
Beginning balance at Dec. 31, 2013	$ 2,366,373		$ 1,571,833	$ 1,362,278	$ (537,279)	$ (30,459)
Increase (Decrease) in Stockholders' Equity
Net income	345,878			345,878
Other comprehensive income (loss)	34,696					34,696
Stock compensation costs	13,883		13,883
Net activity of common stock pursuant to various stock compensation plans and agreements, and related tax benefits (in shares)		368,240
Net activity of common stock pursuant to various stock compensation plans and agreements, and related tax benefits	3,611		14,316		(10,705)
Common stock dividends	(104,015)			(104,015)
Issuance of common stock pursuant to MetroCorp Bancshares, Inc. (“MetroCorp”) acquisition (in shares)		5,583,093
Issuance of common stock pursuant to MetroCorp Bancshares, Inc. (“MetroCorp”) acquisition	190,830		73,044		117,786
Warrant acquired pursuant to MetroCorp acquisition	4,855		4,855
BALANCE (in shares) at Dec. 31, 2014		143,582,229
Ending balance at Dec. 31, 2014	2,856,111		1,677,931	1,604,141	(430,198)	4,237
Increase (Decrease) in Stockholders' Equity
Net income	384,677			384,677
Other comprehensive income (loss)	(19,178)					(19,178)
Stock compensation costs	16,502		16,502
Net activity of common stock pursuant to various stock compensation plans and agreements, and related tax benefits (in shares)		327,004
Net activity of common stock pursuant to various stock compensation plans and agreements, and related tax benefits	1,062		7,026		(5,964)
Common stock dividends	(116,224)			(116,224)
BALANCE (in shares) at Dec. 31, 2015		143,909,233
Ending balance at Dec. 31, 2015	3,122,950		1,701,459	1,872,594	(436,162)	(14,941)
Increase (Decrease) in Stockholders' Equity
Net income	431,677			431,677
Other comprehensive income (loss)	(33,205)					(33,205)
Stock compensation costs	22,102		22,102
Net activity of common stock pursuant to various stock compensation plans and agreements, and related tax benefits (in shares)		258,218
Net activity of common stock pursuant to various stock compensation plans and agreements, and related tax benefits	812		4,037		(3,225)
Common stock dividends	(116,595)			(116,595)
BALANCE (in shares) at Dec. 31, 2016		144,167,451
Ending balance at Dec. 31, 2016	$ 3,427,741		$ 1,727,598	$ 2,187,676	$ (439,387)	$ (48,146)