Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands		Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock at Cost
Beginning balance (in shares) at Dec. 31, 2014			0	35,262,901
Beginning balance at Dec. 31, 2014		$ 1,852,148	$ 0	$ 35,263	$ 1,398,633	$ 496,573	$ 7,525	$ (85,846)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		55,962				55,962
Other comprehensive income		644					644
Cash dividends declared, $0.68 per share		(26,961)				(26,961)
Reclassification of treasury stock under the LBCA (in shares)	[1]			(1,809,497)
Reclassification of treasury stock under the LBCA	[1]	0		$ (1,809)	(84,037)			85,846
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit (in shares)				189,435
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit		1,989		$ 189	1,800			0
Common stock issued for acquisitions (in shares)				7,474,404
Common stock issued for acquisitions		474,753		$ 7,474	467,279
Share-based compensation cost		6,749			6,749
Ending balance (in shares) at Jun. 30, 2015			0	41,117,243
Ending balance at Jun. 30, 2015		2,365,284	$ 0	$ 41,117	1,790,424	525,574	8,169	0
Beginning balance (in shares) at Dec. 31, 2015			8,000	41,139,537
Beginning balance at Dec. 31, 2015		2,498,835	$ 76,812	$ 41,140	1,797,982	584,486	(1,585)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		93,579				93,579
Other comprehensive income		27,569					27,569
Cash dividends declared, $0.68 per share		(28,016)				(28,016)
Preferred stock dividends		(3,430)				(3,430)
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit (in shares)				101,802
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit		(2,262)		$ 102	(2,364)
Preferred stock issued (in shares)			5,750
Preferred stock issued		55,286	$ 55,286
Common stock repurchases (in shares)				(202,506)
Common stock repurchases		(11,666)		$ (203)	(11,463)
Share-based compensation cost		7,702			7,702
Ending balance (in shares) at Jun. 30, 2016			13,750	41,038,833
Ending balance at Jun. 30, 2016		$ 2,637,597	$ 132,098	$ 41,039	$ 1,791,857	$ 646,619	$ 25,984	$ 0

[1] Effective January 1, 2015, companies incorporated in Louisiana became subject to the Louisiana Business Corporation Act (“LBCA”), which eliminates the concept of treasury stock and provides that shares reacquired by a company are to be treated as authorized but unissued. Refer to Note 1, Summary of Significant Accounting Policies, in the Annual Report on Form 10-K for the year ended December 31, 2015, for further discussion.