General and Summary of Significant Accounting Policies Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
NET INCOME PER SHARE
Net Income	$ 20,641	$ 26,563	$ 22,833	$ 30,998	$ (7,355)	$ 219	$ 31,054	$ 4,875	$ 101,035	$ 28,793	$ 68,644
Weighted average number of common shares outstanding (basic)									20,629,000	20,394,000	19,614,000
Weighted Average Number Diluted Shares Outstanding Adjustment									916,000	1,207,000	1,244,000
Weighted Average common and common equivalent shares outstandding (diluted)									21,545,000	21,601,000	20,858,000
Basic	$ 1.00	$ 1.29	$ 1.11	$ 1.51	$ (0.36)	$ 0.01	$ 1.53	$ 0.24	$ 4.90	$ 1.41	$ 3.50
Diluted	$ 0.96	$ 1.24	$ 1.06	$ 1.44	$ (0.36)	$ 0.01	$ 1.44	$ 0.23	$ 4.69	$ 1.33	$ 3.29
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									10,760	5,300	337