Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		Total	Common Stock Outstanding	Common Stock	Value of Shares Held in Rabbi Trust at Cost	Deferred Compensation Obligation	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2016		$ 864,690		$ 268	$ (4,277)	$ 4,277	$ 451,664	$ 414,095	$ (1,337)
Beginning balance (in shares) at Dec. 31, 2016			27,005,813
Net income		87,204						$ 87,204
Other comprehensive loss		(494)							(494)
Common Stock, Dividends, Per Share, Declared								$ 1.28
Common dividend declared		(34,997)						$ (34,997)
Common stock issued for acquisition		23,468		4			23,464
Common stock issued for acquisition (in shares)			369,286
Proceeds from exercise of stock options, net of cash paid		214					214
Proceeds from exercise of stock options (in shares)			19,340
Stock based compensation		3,333					3,333
Restricted stock awards issued, net of awards surrendered (in shares)			31,665
Restricted stock awards issued, net of awards surrendered		(1,422)		1			(1,423)
Stock Issued During Period, Shares, Other			24,086
Stock Issued During Period, Value, Other		1,636					1,636
Increase (Decrease) in Deferred Compensation					(313)	313
Ending balance (in shares) at Dec. 31, 2017			27,450,190
Ending balance at Dec. 31, 2017		943,809		273	(4,590)	4,590	479,430	465,937	(1,831)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	[1]	177					542	(365)
Prior Period Reclassification Adjustment	[2]	0						397	(397)
Net income		121,622						$ 121,622
Other comprehensive loss		1,886							1,886
Common Stock, Dividends, Per Share, Declared								$ 1.52
Common dividend declared		(42,051)						$ (42,051)
Common stock issued for acquisition		42,474		5			42,469
Common stock issued for acquisition (in shares)			528,353
Proceeds from exercise of stock options, net of cash paid		184		0			184
Proceeds from exercise of stock options (in shares)			23,195
Stock based compensation		4,225					4,225
Restricted stock awards issued, net of awards surrendered (in shares)			43,383
Restricted stock awards issued, net of awards surrendered		(1,371)		1			(1,372)
Stock Issued During Period, Shares, Other			35,287
Stock Issued During Period, Value, Other		2,712					2,712
Increase (Decrease) in Deferred Compensation		0
Increase (Decrease) in Deferred Compensation and Other Retirement Benefits					(128)	128
Ending balance (in shares) at Dec. 31, 2018			28,080,408
Ending balance at Dec. 31, 2018		1,073,490		279	(4,718)	4,718	527,648	546,736	(1,173)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	[3]	0
Net income		29,934
Ending balance (in shares) at Dec. 31, 2018			28,080,408
Ending balance at Dec. 31, 2018		1,073,490		279	(4,718)	4,718	527,648	546,736	(1,173)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	[3]							831	(831)
Net income		165,175						$ 165,175
Other comprehensive loss		19,342							19,342
Common Stock, Dividends, Per Share, Declared								$ 1.76
Common dividend declared		(57,729)						$ (57,729)
Common stock issued for acquisition		499,693		61			499,632
Common stock issued for acquisition (in shares)			6,166,010
Proceeds from exercise of stock options, net of cash paid		281					281
Proceeds from exercise of stock options (in shares)			14,646
Stock based compensation		4,403					4,403
Restricted stock awards issued, net of awards surrendered (in shares)			50,080
Restricted stock awards issued, net of awards surrendered		(1,463)		1			(1,464)
Stock Issued During Period, Shares, Other			66,244
Stock Issued During Period, Value, Other		4,951		1			4,950
Increase (Decrease) in Deferred Compensation		0
Increase (Decrease) in Deferred Compensation and Other Retirement Benefits					(17)	17
Ending balance (in shares) at Dec. 31, 2019			34,377,388
Ending balance at Dec. 31, 2019		$ 1,708,143		$ 342	$ (4,735)	$ 4,735	$ 1,035,450	$ 654,182	$ 18,169

[1] Represents adjustment needed to reflect the cumulative impact on retained earnings for previously recognized stock based compensation, which included an adjustment for estimated forfeitures. Pursuant to the Company's adoption of Accounting Standards Update 2016-09, the Company has elected to recognize stock based compensation without inclusion of a forfeiture estimate, and as such has recognized this adjustment to present retained earnings consistent with this election.

[2] Represents adjustment needed to reflect the cumulative impact on retained earnings for reclassification of the income tax effects attributable to accumulated other comprehensive income, as a result of the Tax Cuts and Jobs Act (the "Tax Act"). Pursuant to the Company's adoption of Accounting Standards Update 2018-02, the Company has elected to reclassify amounts stranded in other comprehensive income to retained earnings.

[3] Represents adjustment needed to reflect the cumulative impact on retained earnings for the classification and measurement of investments in equity securities. Pursuant to the Company's adoption of Accounting Standards Update 2016-01, the Company's investments in equity securities will no longer be classified as available for sale, therefore the Company was required to reclassify the net unrealized gain recognized on the change in fair value of these equity securities from other comprehensive income to retained earnings.