CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Retained earnings	Accumulated other comprehensive income (loss)	Treasury stock
Beginning Balances (in shares) at Dec. 31, 2017		68,730,731			(6,661,644)
Beginning Balances at Dec. 31, 2017	$ 930,664	$ 573,109	$ 491,847	$ (20,390)	$ (113,902)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0		5,093	(5,093)
Net income	66,924		66,924
Other comprehensive income (loss)	(17,676)			(17,676)
Cash dividends declared :
Common stock at $0.22 per share and $0.44 per share in 2019 and $0.19 per share and $0.38 per share in 2018	(30,394)		(30,394)
Stock Issued During Period, Shares, Acquisitions		35,551,063.000
Stock Issued During Period, Value, Acquisitions	1,045,876	$ 1,045,876
Stock Options and Warrants Acquired And Converted Pursuant To Acquisition	16,037	16,037
Stock Issued During Period, Shares, Other					53,907
Adjustments to Additional Paid in Capital, Other	0	(922)			$ 922
Exercise of stock options, net of shares purchased (in shares)					31,554
Exercise of stock options, net of shares purchased	267	(275)			$ 542
Restricted stock awards, net of forfeitures (in shares)					199,286
Restricted stock awards, net of forfeitures	(2,207)	(4,699)			$ 2,492
Share-based compensation expense	3,446	$ 3,446
Ending Balances (in shares) at Jun. 30, 2018		104,281,794			(6,376,897)
Ending Balances at Jun. 30, 2018	2,012,937	$ 1,632,572	533,470	(43,159)	$ (109,946)
Beginning Balances (in shares) at Mar. 31, 2018		68,730,731			(6,516,908)
Beginning Balances at Mar. 31, 2018	939,985	$ 571,457	515,649	(34,834)	$ (112,287)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	36,418		36,418
Other comprehensive income (loss)	(8,325)			(8,325)
Cash dividends declared :
Common stock at $0.22 per share and $0.44 per share in 2019 and $0.19 per share and $0.38 per share in 2018	(18,597)		(18,597)
Stock Issued During Period, Shares, Acquisitions		35,551,063.000
Stock Issued During Period, Value, Acquisitions	1,045,876	$ 1,045,876
Stock Options and Warrants Acquired And Converted Pursuant To Acquisition	16,037	16,037
Stock Issued During Period, Shares, Other					52,479
Adjustments to Additional Paid in Capital, Other	0	(898)			$ 898
Exercise of stock options, net of shares purchased (in shares)					19,754
Exercise of stock options, net of shares purchased	130	(210)			$ 340
Restricted stock awards, net of forfeitures (in shares)					67,778
Restricted stock awards, net of forfeitures	(79)	(1,182)			$ 1,103
Share-based compensation expense	1,492	$ 1,492
Ending Balances (in shares) at Jun. 30, 2018		104,281,794			(6,376,897)
Ending Balances at Jun. 30, 2018	2,012,937	$ 1,632,572	533,470	(43,159)	$ (109,946)
Beginning Balances (in shares) at Dec. 31, 2018		104,281,794			(6,387,508)
Beginning Balances at Dec. 31, 2018	2,078,249	$ 1,633,256	600,014	(44,408)	$ (110,613)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	3,542		2,636	906
Net income	98,542		98,542
Other comprehensive income (loss)	48,695			48,695
Cash dividends declared :
Common stock at $0.22 per share and $0.44 per share in 2019 and $0.19 per share and $0.38 per share in 2018	(43,462)		(43,462)
Stock Issued During Period, Shares, Other					452,134
Adjustments to Additional Paid in Capital, Other	0	(7,830)			$ 7,830
Exercise of stock options, net of shares purchased (in shares)					20,424
Exercise of stock options, net of shares purchased	90	(264)			$ 354
Restricted stock awards, net of forfeitures (in shares)					280,846
Restricted stock awards, net of forfeitures	(2,229)	(6,225)			$ 3,996
Share-based compensation expense	4,762	$ 4,762
Ending Balances (in shares) at Jun. 30, 2019		104,281,794			(5,634,104)
Ending Balances at Jun. 30, 2019	2,188,189	$ 1,623,699	657,730	5,193	$ (98,433)
Beginning Balances (in shares) at Mar. 31, 2019		104,281,794			(5,667,922)
Beginning Balances at Mar. 31, 2019	2,130,419	$ 1,622,554	626,408	(19,635)	$ (98,908)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	415		415
Net income	52,703		52,703
Other comprehensive income (loss)	24,828			24,828
Cash dividends declared :
Common stock at $0.22 per share and $0.44 per share in 2019 and $0.19 per share and $0.38 per share in 2018	(21,796)		(21,796)
Restricted stock awards, net of forfeitures (in shares)					33,818
Restricted stock awards, net of forfeitures	(146)	(621)			$ 475
Share-based compensation expense	1,766	$ 1,766
Ending Balances (in shares) at Jun. 30, 2019		104,281,794			(5,634,104)
Ending Balances at Jun. 30, 2019	$ 2,188,189	$ 1,623,699	$ 657,730	$ 5,193	$ (98,433)