Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Income from continuing operations									$ 56,641	$ 80,509	$ 86,477
Loss from discontinued operations (see Note 6)									(23,797)	0	0
Net income	$ 9,971	$ 15,003	$ 17,570	$ (9,700)	$ 17,883	$ 20,299	$ 20,660	$ 21,667	$ 32,844	$ 80,509	$ 86,477
Weighted average shares outstanding - basic and diluted (in shares)									5,116,838	5,115,501	5,114,084
Income from continuing operations - basic and diluted (in usd per share)									$ 11.07	$ 15.74	$ 16.91
Loss from discontinued operations (see Note 6) - basic and diluted (in usd per share)									(4.65)	0.00	0.00
Net income per common share - basic and diluted (in dollars per share)									$ 6.42	$ 15.74	$ 16.91