Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Retained Earnings (Accumulated Deficit) [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]
Balance at Dec. 31, 2019	$ 1,184,472	$ (1,975)	$ 132	$ 1,209,120	$ (24,780)	$ (1,975)
Balance, Shares at Dec. 31, 2019			132,015,635
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	26,469				26,469
Dividends	(31,700)				(31,700)
Issuance of shares for vested restricted stock units (in shares)			95,694
Stock-based compensation expense for restricted stock units	914			914
Balance at Mar. 31, 2020	1,178,180		$ 132	1,210,034	(31,986)
Balance, Shares at Mar. 31, 2020			132,111,329
Balance at Dec. 31, 2019	1,184,472	(1,975)	$ 132	1,209,120	(24,780)	$ (1,975)
Balance, Shares at Dec. 31, 2019			132,015,635
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	42,313	4,700
Balance at Jun. 30, 2020	1,171,198		$ 132	1,211,001	(39,935)
Balance, Shares at Jun. 30, 2020			132,231,184
Balance at Mar. 31, 2020	1,178,180		$ 132	1,210,034	(31,986)
Balance, Shares at Mar. 31, 2020			132,111,329
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	15,844	$ 3,900			15,844
Dividends	(23,793)				(23,793)
Issuance of shares for vested restricted stock units (in shares)			119,855
Stock-based compensation expense for restricted stock units	967			967
Balance at Jun. 30, 2020	1,171,198		$ 132	1,211,001	(39,935)
Balance, Shares at Jun. 30, 2020			132,231,184
Balance at Dec. 31, 2020	1,174,421		$ 132	1,213,987	(39,698)
Balance, Shares at Dec. 31, 2020			132,532,383
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	20,381				20,381
Dividends	(27,838)				(27,838)
Issuance of shares for vested restricted stock units (in shares)			34,027
Stock-based compensation expense for restricted stock units	737			737
Balance at Mar. 31, 2021	1,167,701		$ 132	1,214,724	(47,155)
Balance, Shares at Mar. 31, 2021			132,566,410
Balance at Dec. 31, 2020	1,174,421		$ 132	1,213,987	(39,698)
Balance, Shares at Dec. 31, 2020			132,532,383
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	38,633
Balance at Jun. 30, 2021	1,158,899		$ 132	1,215,513	(56,746)
Balance, Shares at Jun. 30, 2021			132,634,672
Balance at Mar. 31, 2021	1,167,701		$ 132	1,214,724	(47,155)
Balance, Shares at Mar. 31, 2021			132,566,410
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	18,252				18,252
Dividends	(27,843)				(27,843)
Issuance of shares for vested restricted stock units (in shares)			77,766
Restricted stock units withheld for tax liability	(135)			(135)
Restricted stock units withheld for tax liability (in shares)			(9,504)
Stock-based compensation expense for restricted stock units	924			924
Balance at Jun. 30, 2021	$ 1,158,899		$ 132	$ 1,215,513	$ (56,746)
Balance, Shares at Jun. 30, 2021			132,634,672