Statements of Change in Common Stock Equity Statement - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss), Net of Tax	Treasury Stock	Restricted Stock	Restricted Stock Additional Paid-in Capital	Performance Shares	Performance Shares Additional Paid-in Capital
Balances at beginning of period (in shares) at Dec. 31, 2018		65,828,688				25,147,567
Balances at beginning of period at Dec. 31, 2018	$ 1,164,103	$ 65,829	$ 328,480	$ 1,227,471	$ (38,784)	$ (418,893)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation grants of common stock, value							$ (804)	$ (1,328)	$ 2,143	$ 1,478
Stock based compensation, grants of common stock, treasury stock reissued (in share)							(31,461)		(39,923)
Stock based compensation, grants of common stock, treasury stock reissued, value							$ 524		$ 665
Stock awards withheld for taxes (in shares)						12,425
Stock awards withheld for taxes, value	(637)		(430)			$ (207)
Forfeited restricted common stock (in shares)						2,566
Forfeited restricted common stock, value	(43)					$ (43)
Compensation paid in shares (in shares)						(669)
Compensation paid in shares, value	39		28			$ 11
Net income (loss)	6,089			6,089
Other Comprehensive Income (Loss)	1,657				1,657
Common stock, dividends declared, cash	(14,658)			(14,658)
Balances at end of period (in shares) at Mar. 31, 2019		65,828,688				25,090,505
Balances at end of period at Mar. 31, 2019	1,157,889	$ 65,829	328,228	1,218,902	(37,127)	$ (417,943)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	81,739
Common stock, dividends declared, cash	$ (62,700)
Balances at end of period (in shares) at Mar. 31, 2020	64,312,516	64,428,688				23,656,061
Balances at end of period at Mar. 31, 2020	$ 1,165,811	$ 64,429	322,890	1,221,513	(48,977)	$ (394,044)
Balances at beginning of period (in shares) at Dec. 31, 2019	64,332,884	64,428,688				23,696,262
Balances at beginning of period at Dec. 31, 2019	$ 1,216,547	$ 64,429	323,367	1,272,418	(48,952)	$ (394,715)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation grants of common stock, value							$ 299	$ (40)	$ 732	$ 197
Stock based compensation, grants of common stock, treasury stock reissued (in share)							(20,368)		(32,119)
Stock based compensation, grants of common stock, treasury stock reissued, value							$ 339		$ 535
Stock awards withheld for taxes (in shares)						12,404
Stock awards withheld for taxes, value	(846)		(640)			$ (206)
Compensation paid in shares (in shares)						(118)
Compensation paid in shares, value	9		6			$ 3
Net income (loss)	(35,209)			(35,209)
Other Comprehensive Income (Loss)	(25)				(25)
Common stock, dividends declared, cash	$ (15,696)			(15,696)
Balances at end of period (in shares) at Mar. 31, 2020	64,312,516	64,428,688				23,656,061
Balances at end of period at Mar. 31, 2020	$ 1,165,811	$ 64,429	$ 322,890	$ 1,221,513	$ (48,977)	$ (394,044)