Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock Outstanding [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Common Stock Outstanding [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Common Stock Outstanding [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2018					56,615,352				56,615,352
Balance at Dec. 31, 2018	$ 0	$ 0	$ (67)	$ (67)	$ 566	$ 1,168,442	$ 406,925	$ 1,575,933	$ 566	$ 1,168,442	$ 406,992	$ 1,576,000
Net Income									$ 0	0	40,550	40,550
Shares issued under stock-based compensation programs, net (in shares)									372,344
Shares issued under stock-based compensation programs, net									$ 4	7,083	0	7,087
Cash dividends declared									0	0	(17,019)	(17,019)
Stock-based compensation expense									$ 0	4,251	0	4,251
Forfeiture of restricted stock (in shares)									(1,714)
Forfeiture of restricted stock									$ 0	0	0	0
Stock dividend declared (in shares)									4,534,908
Stock dividend declared									$ 45	138,950	(139,091)	(96)
Balance (in shares) at Mar. 31, 2019									61,520,890
Balance at Mar. 31, 2019									$ 615	1,318,726	291,365	1,610,706
Balance (in shares) at Dec. 31, 2019					62,574,961				62,574,961
Balance at Dec. 31, 2019	$ 0	$ 0	$ (34)	$ (34)	$ 626	$ 1,348,733	$ 433,092	$ 1,782,451	$ 626	1,348,733	433,126	1,782,485
Net Income									$ 0	0	36,760	36,760
Shares issued under stock-based compensation programs, net (in shares)									477,582
Shares issued under stock-based compensation programs, net									$ 5	8,189	0	8,194
Cash dividends declared									0	0	(20,768)	(20,768)
Stock-based compensation expense									$ 0	4,440	0	4,440
Forfeiture of restricted stock (in shares)									(48)
Forfeiture of restricted stock									$ 0	0	0	0
Balance (in shares) at Mar. 31, 2020									63,052,495
Balance at Mar. 31, 2020									$ 631	$ 1,361,362	$ 449,084	$ 1,811,077