Earnings per Weighted Average Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings per Weighted Average Common Share
Net income from continuing operations	$ 44,742	$ 42,494	$ (1,990)	$ 15,619	$ 25,934	$ 29,946	$ 85,246	$ 71,499
Allocation of income for participating shares	(201)			(80)			(392)	(378)
Net income from continuing operations attributed to common shareholders	$ 44,541			$ 15,539			$ 84,854	$ 71,121
Total weighted average common shares outstanding, including participating shares	14,974,636			15,299,689			15,155,969	15,275,322
Less: weighted average participating shares	(66,827)			(78,787)			(70,055)	(80,853)
Basic earnings per share denominator	14,907,809			15,220,902			15,085,914	15,194,469
Common equivalent shares- non-vested performance stock grants	122,468			140,006			118,241	142,862
Diluted earnings per share denominator	15,030,277			15,360,908			15,204,155	15,337,331
Basic earnings per share (in dollars per share)	$ 2.99			$ 1.02			$ 5.62	$ 4.68
Diluted earnings per share (in dollars per share)	2.96			1.01			5.58	4.64
Undistributed earnings attributable to common shareholders - basic and diluted:
Net income from continuing operations attributable to common shareholders -Basic	2.99			1.02			5.62	4.68
Dividends declared	(0.90)			(0.90)			(2.70)	(2.50)
Undistributed earnings	2.09			0.12			2.92	2.18
Undistributed earnings attributable to common shareholders - diluted
Net income from continuing operations attributable to common shareholders -Diluted	2.96			1.01			5.58	4.64
Dividends declared	(0.90)			(0.90)			(2.70)	(2.50)
Undistributed earnings	$ 2.06			$ 0.11			$ 2.88	$ 2.14
Antidilutive common shares	4						0	0