Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Revision of Prior Period, Reclassification, Adjustment [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Common Stock [Member] Revision of Prior Period, Reclassification, Adjustment [Member]	Common Stock [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Surplus [Member]	Surplus [Member] Revision of Prior Period, Reclassification, Adjustment [Member]	Surplus [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Retained Earnings [Member]	Retained Earnings [Member] Revision of Prior Period, Reclassification, Adjustment [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Revision of Prior Period, Reclassification, Adjustment [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Treasury Stock [Member]	Treasury Stock [Member] Revision of Prior Period, Reclassification, Adjustment [Member]	Treasury Stock [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]
Beginning Balance at Dec. 31, 2018	$ 3,251,624	$ 50	$ (1,049)	$ 263,098	$ 0	$ 0	$ 2,134,462	$ 0	$ 0	$ 1,013,037	$ 0	$ (1,049)	$ (57,019)	$ 50	$ 0	$ (101,954)	$ 0	$ 0
Beginning Balance, shares at Dec. 31, 2018				105,239,121
Net income	63,642			$ 0			0			63,642			0			0
Other comprehensive income, net of tax	17,699			0			0			0			17,699			0
Comprehensive income, net of tax	81,341
Stock based compensation expense	1,113			0			1,113			0			0			0
Purchase of treasury stock	(12,072)			0			0			0			0			(12,072)
Cash dividends	(34,759)			0			0			(34,759)			0			0
Grant of restricted stock	0			$ 316			(316)			0			0			0
Grant of restricted stock, shares				126,427
Common stock options exercised	643			$ 84			559			0			0			0
Common stock options exercised, shares				33,816
Ending Balance at Mar. 31, 2019	3,286,891			$ 263,498			2,135,818			1,040,871			(39,270)			(114,026)
Ending Balance, shares at Mar. 31, 2019				105,399,364
Beginning Balance at Dec. 31, 2018	3,251,624	$ 50	(1,049)	$ 263,098	$ 0	0	2,134,462	$ 0	0	1,013,037	$ 0	(1,049)	(57,019)	$ 50	0	(101,954)	$ 0	0
Beginning Balance, shares at Dec. 31, 2018				105,239,121
Net income	130,849
Other comprehensive income, net of tax	36,602
Comprehensive income, net of tax	$ 167,451
Common stock options exercised, shares	47,960
Ending Balance at Jun. 30, 2019	$ 3,333,858			$ 263,534			2,137,459			1,073,390			(20,367)			(120,158)
Ending Balance, shares at Jun. 30, 2019				105,413,508
Beginning Balance at Mar. 31, 2019	3,286,891			$ 263,498			2,135,818			1,040,871			(39,270)			(114,026)
Beginning Balance, shares at Mar. 31, 2019				105,399,364
Net income	67,207			$ 0			0			67,207			0			0
Other comprehensive income, net of tax	18,903			0			0			0			18,903			0
Comprehensive income, net of tax	86,110
Stock based compensation expense	1,198			0			1,198			0			0			0
Purchase of treasury stock	(6,032)			0			0			0			0			(6,032)
Cash dividends	(34,688)			0			0			(34,688)			0			0
Forfeiture of restricted stock	0			0			100			0			0			(100)
Common stock options exercised	379			$ 36			343			0			0			0
Common stock options exercised, shares				14,144
Ending Balance at Jun. 30, 2019	3,333,858			$ 263,534			2,137,459			1,073,390			(20,367)			(120,158)
Ending Balance, shares at Jun. 30, 2019				105,413,508
Beginning Balance at Dec. 31, 2019	$ 3,363,833		(44,331)	$ 263,736		0	2,140,175		0	1,132,579		(44,331)	(34,869)		0	(137,788)		0
Beginning Balance, shares at Dec. 31, 2019				105,494,290
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Net income	$ 40,183			$ 0			0			40,183			0			0
Other comprehensive income, net of tax	18,698			0			0			0			18,698			0
Comprehensive income, net of tax	58,881
Stock based compensation expense	1,253			0			1,253			0			0			0
Purchase of treasury stock	(608)			0			0			0			0			(608)
Cash dividends	(35,604)			0			0			(35,604)			0			0
Grant of restricted stock	0			$ 439			(439)			0			0			0
Grant of restricted stock, shares				175,495
Forfeiture of restricted stock	0			$ 0			35			0			0			(35)
Common stock options exercised	278			$ 36			242			0			0			0
Common stock options exercised, shares				14,694
Ending Balance at Mar. 31, 2020	3,343,702			$ 264,211			2,141,266			1,092,827			(16,171)			(138,431)
Ending Balance, shares at Mar. 31, 2020				105,684,479
Beginning Balance at Dec. 31, 2019	3,363,833		$ (44,331)	$ 263,736		$ 0	2,140,175		$ 0	1,132,579		$ (44,331)	(34,869)		$ 0	(137,788)		$ 0
Beginning Balance, shares at Dec. 31, 2019				105,494,290
Net income	92,869
Other comprehensive income, net of tax	46,373												46,373
Comprehensive income, net of tax	$ 139,242
Common stock options exercised, shares	14,994
Ending Balance at Jun. 30, 2020	$ 4,197,855			$ 334,291			2,890,394			1,100,097			11,504			(138,431)
Ending Balance, shares at Jun. 30, 2020				133,716,280
Beginning Balance at Mar. 31, 2020	3,343,702			$ 264,211			2,141,266			1,092,827			(16,171)			(138,431)
Beginning Balance, shares at Mar. 31, 2020				105,684,479
Net income	52,686			$ 0			0			52,686			0			0
Other comprehensive income, net of tax	27,675			0			0			0			27,675			0
Comprehensive income, net of tax	80,361
Stock based compensation expense	1,369			0			1,369			0			0			0
Acquisition, Values	817,830			$ 70,079			747,751			0			0			0
Acquisition, Shares				28,031,501
Purchase of treasury stock	0			$ 0			0			0			0			0
Cash dividends	(45,416)			0			0			(45,416)			0			0
Common stock options exercised	9			$ 1			8			0			0			0
Common stock options exercised, shares				300
Ending Balance at Jun. 30, 2020	$ 4,197,855			$ 334,291			$ 2,890,394			$ 1,100,097			$ 11,504			$ (138,431)
Ending Balance, shares at Jun. 30, 2020				133,716,280