Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]
BALANCE at Dec. 31, 2017	$ 3,824,154	$ 69,491	$ 2,035,219	$ 1,719,557	$ (113)
BALANCE (in shares) at Dec. 31, 2017		69,490,910
Net income	155,958			155,958
Other comprehensive income	458				458
Common stock issued in connection with the issuance of restricted stock awards, net		$ 347	(347)
Common stock issued in connection with the issuance of restricted stock awards, net (in shares)		347,276
Stock based compensation expense	5,160		5,160
Cash dividends declared	(50,278)			(50,278)
BALANCE at Jun. 30, 2018	3,935,452	$ 69,838	2,040,032	1,825,237	345
BALANCE (in shares) at Jun. 30, 2018		69,838,186
BALANCE at Mar. 31, 2018	3,876,145	$ 69,819	2,037,498	1,768,783	45
BALANCE (in shares) at Mar. 31, 2018		69,819,286
Net income	81,597			81,597
Other comprehensive income	300				300
Common stock issued in connection with the issuance of restricted stock awards, net		$ 19	(19)
Common stock issued in connection with the issuance of restricted stock awards, net (in shares)		18,900
Stock based compensation expense	2,553		2,553
Cash dividends declared	(25,143)			(25,143)
BALANCE at Jun. 30, 2018	3,935,452	$ 69,838	2,040,032	1,825,237	345
BALANCE (in shares) at Jun. 30, 2018		69,838,186
BALANCE at Dec. 31, 2018	4,052,824	$ 69,847	2,045,351	1,937,316	310
BALANCE (in shares) at Dec. 31, 2018		69,846,825
Net income	164,660			164,660
Other comprehensive income	963				963
Common stock issued in connection with the issuance of restricted stock awards, net		$ 13	(13)
Common stock issued in connection with the issuance of restricted stock awards, net (in shares)		13,434
Common stock repurchase	(38,421)	$ (599)	(37,822)
Common stock repurchase (in shares)		(598,828)
Stock based compensation expense	5,149		5,149
Cash dividends declared	(57,280)			(57,280)
BALANCE at Jun. 30, 2019	4,127,895	$ 69,261	2,012,665	2,044,696	1,273
BALANCE (in shares) at Jun. 30, 2019		69,261,431
BALANCE at Mar. 31, 2019	4,109,790	$ 69,846	2,048,156	1,991,081	707
BALANCE (in shares) at Mar. 31, 2019		69,845,925
Net income	82,258			82,258
Other comprehensive income	566				566
Common stock issued in connection with the issuance of restricted stock awards, net		$ 14	(14)
Common stock issued in connection with the issuance of restricted stock awards, net (in shares)		14,334
Common stock repurchase	(38,421)	$ (599)	(37,822)
Common stock repurchase (in shares)		(598,828)
Stock based compensation expense	2,345		2,345
Cash dividends declared	(28,643)			(28,643)
BALANCE at Jun. 30, 2019	$ 4,127,895	$ 69,261	$ 2,012,665	$ 2,044,696	$ 1,273
BALANCE (in shares) at Jun. 30, 2019		69,261,431