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		98,437				98,437
Other comprehensive income		9,458					9,458
Cash dividends declared		(40,945)				(40,945)
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)				200,958
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit		1,748		$ 201	1,547			0
Preferred stock issued (in shares)			8,000
Preferred stock issued		77,463	$ 77,463		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		10,139			10,139
Ending balance (in shares) at Sep. 30, 2015			8,000	41,128,766
Ending balance at Sep. 30, 2015		2,483,201	$ 77,463	$ 41,129	1,793,561	554,065	16,983	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		141,647				141,647
Other comprehensive income		21,373					21,373
Cash dividends declared		(42,805)				(42,805)
Preferred stock dividends		(7,020)				(7,020)
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit (in shares)				144,670
Common stock issued under incentive plans, net of shares surrendered in payment, including tax benefit		232		$ 145	87
Preferred stock issued (in shares)			5,750
Preferred stock issued		55,285	$ 55,285
Common stock repurchases (in shares)				(202,506)
Common stock repurchases		(11,666)		$ (203)	(11,463)
Share-based compensation cost		11,229			11,229
Ending balance (in shares) at Sep. 30, 2016			13,750	41,081,701
Ending balance at Sep. 30, 2016		$ 2,667,110	$ 132,097	$ 41,082	$ 1,797,835	$ 676,308	$ 19,788	$ 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.