Consolidated Statements of Changes in Shareholders' Equity - (Unaudited) - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid In Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2019			33,241,496,000
Beginning balance at Dec. 31, 2019	$ 1,190,681	$ (10,931)	$ 331	$ 482,286	$ 705,105	$ (10,931)	$ 2,959
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	51,979				51,979
Other comprehensive loss, net of tax	11,709						11,709
Stock-based compensation expense	2,423			2,423
Vesting of time based stock awards issued at date of grant, net of shares withheld for payroll taxes (in shares)			(24,921,000)
Vesting of performance based stock awards, net of shares withheld for payroll taxes (in shares)			4,126,000
Time based stock awards granted (in shares)			176,252,000
Issuance of common stock related to employee stock purchase plan (in shares)			10,644,000
Issuance of common stock related to employee stock purchase plan	382			382
Cash dividends declared	(14,180)				(14,180)
Common stock repurchased (in shares)			(1,182,841,000)
Common stock repurchased	(44,168)		$ (11)	(44,157)
Ending balance (in shares) at Jun. 30, 2020			32,224,756,000
Ending balance at Jun. 30, 2020	$ 1,187,895		$ 320	440,934	731,973		14,668
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared (in dollars per share)	$ 0.44
Beginning balance (in shares) at Mar. 31, 2020			32,197,258,000
Beginning balance at Mar. 31, 2020	$ 1,162,778		$ 320	439,321	710,072		13,065
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	28,856				28,856
Other comprehensive loss, net of tax	1,603						1,603
Stock-based compensation expense	1,427			1,427
Vesting of time based stock awards issued at date of grant, net of shares withheld for payroll taxes (in shares)			(2,738,000)
Time based stock awards granted (in shares)			24,068,000
Issuance of common stock related to employee stock purchase plan (in shares)			6,168,000
Issuance of common stock related to employee stock purchase plan	186			186
Cash dividends declared	(6,955)				(6,955)
Ending balance (in shares) at Jun. 30, 2020			32,224,756,000
Ending balance at Jun. 30, 2020	$ 1,187,895		$ 320	440,934	731,973		14,668
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared (in dollars per share)	$ 0.22
Beginning balance (in shares) at Dec. 31, 2020	31,779,663		31,779,663,000
Beginning balance at Dec. 31, 2020	$ 1,240,892		$ 315	427,016	798,061		15,500
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	91,462				91,462
Other comprehensive loss, net of tax	(10,980)						(10,980)
Stock-based compensation expense	3,823			3,823
Vesting of time based stock awards issued at date of grant, net of shares withheld for payroll taxes (in shares)			(20,999,000)
Vesting of time based stock awards issued at date of grant, net of shares withheld for payroll taxes	0		$ 1	(1)
Vesting of performance based stock awards, net of shares withheld for payroll taxes (in shares)			15,686,000
Time based stock awards granted (in shares)			178,922,000
Issuance of common stock related to employee stock purchase plan (in shares)			9,767,000
Issuance of common stock related to employee stock purchase plan	327			327
Cash dividends declared	(19,126)				(19,126)
Common stock repurchased (in shares)			(1,466,000)
Common stock repurchased	$ (62)		$ 0	(62)
Ending balance (in shares) at Jun. 30, 2021	31,961,573		31,961,573,000
Ending balance at Jun. 30, 2021	$ 1,306,336		$ 316	431,103	870,397		4,520
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared (in dollars per share)	$ 0.6
Beginning balance (in shares) at Mar. 31, 2021			31,960,379,000
Beginning balance at Mar. 31, 2021	$ 1,260,833		$ 316	428,917	833,598		(1,998)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	47,993				47,993
Other comprehensive loss, net of tax	6,518						6,518
Stock-based compensation expense	1,998			1,998
Vesting of time based stock awards issued at date of grant, net of shares withheld for payroll taxes (in shares)			(4,336,000)
Time based stock awards granted (in shares)			921,000
Issuance of common stock related to employee stock purchase plan (in shares)			4,609,000
Issuance of common stock related to employee stock purchase plan	188			188
Cash dividends declared	$ (11,194)				(11,194)
Ending balance (in shares) at Jun. 30, 2021	31,961,573		31,961,573,000
Ending balance at Jun. 30, 2021	$ 1,306,336		$ 316	$ 431,103	$ 870,397		$ 4,520
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared (in dollars per share)	$ 0.35