Earnings Per Share - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Line Items]
Net income from continuing operations	$ (724)	$ (5,132)	$ 58,793	$ 43,144
Loss from discontinued operations, net of tax	0	280	0	(498)
Net income	$ (724)	$ (4,852)	$ 58,793	$ 42,646
Average common shares outstanding:
Average common shares outstanding - basic (in shares)	30,664	30,537	30,639	30,514
Additional shares for stock-based compensation plans	0	0	32	45
Average common shares outstanding - diluted (in shares)	30,664	30,537	30,671	30,559
Earnings from continuing operations per share of common stock:
Basic (in dollars per share)	$ (0.02)	$ (0.17)	$ 1.92	$ 1.41
Diluted (in dollars per share)	(0.02)	(0.17)	1.92	1.41
Loss from discontinued operations per share of common stock:
Basic (in dollars per share)	0	0.01	0	(0.01)
Diluted (in dollars per share)	0	0.01	0	(0.01)
Earnings (loss) per share of common stock
Basic (in dollars per share)	(0.02)	(0.16)	1.92	1.40
Diluted (in dollars per share)	$ (0.02)	$ (0.16)	$ 1.92	$ 1.40
Antidilutive shares	48	41	7	0
Discontinued Operations, Held-for-sale [Member] | Gill Ranch [Member]
Income Statement [Line Items]
Loss from discontinued operations, net of tax		$ 280		$ (498)
Loss from discontinued operations per share of common stock:
Basic (in dollars per share)	$ 0	$ 0.01	$ 0	$ (0.01)
Diluted (in dollars per share)	$ 0	$ 0.01	$ 0	$ (0.01)