Earnings per Weighted Average Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings per Weighted Average Common Share
Net income from continuing operations	$ 42,494	$ (1,990)	$ 25,934	$ 29,946	$ 40,504	$ 55,880
Allocation of income for participating shares	(195)		(134)		(190)	(300)
Net income from continuing operations attributed to common shareholders	$ 42,299		$ 25,800		$ 40,314	$ 55,580
Total weighted average common shares outstanding, including participating shares	15,189,442		15,299,691		15,247,100	15,262,937
Less: weighted average participating shares	(69,403)		(78,869)		(71,691)	(81,903)
Basic earnings per share denominator	15,120,039		15,220,822		15,175,409	15,181,034
Common equivalent shares- non-vested performance stock grants	117,256		125,412		116,777	145,087
Diluted earnings per share denominator	15,237,295		15,346,234		15,292,186	15,326,121
Basic earnings per share (in dollars per share)	$ 2.80		$ 1.70		$ 2.66	$ 3.66
Diluted earnings per share (in dollars per share)	2.78		1.68		2.64	3.63
Undistributed earnings attributable to common shareholders - basic and diluted:
Net income from continuing operations attributable to common shareholders -Basic	2.80		1.70		2.66	3.66
Dividends declared	(0.90)		(0.80)		(1.80)	(1.60)
Undistributed earnings	1.90		0.90		0.86	2.06
Undistributed earnings attributable to common shareholders - diluted
Net income from continuing operations attributable to common shareholders -Diluted	2.78		1.68		2.64	3.63
Dividends declared	(0.90)		(0.80)		(1.80)	(1.60)
Undistributed earnings	$ 1.88		$ 0.88		$ 0.84	$ 2.03
Antidilutive common shares	2,310		0		106	0