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, 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
NET INCOME PER SHARE
Net Income	$ (7,355)	$ 219	$ 31,054	$ 4,875	$ 49,705	$ 136	$ (37,060)	$ 55,863	$ 28,793	$ 68,644	$ 63,084
Weighted average number of common shares outstanding (basic)									20,394,000	19,614,000	16,168,000
Weighted Average Number Diluted Shares Outstanding Adjustment									1,207,000	1,244,000	1,086,000
Weighted Average common and common equivalent shares outstandding (diluted)									21,601,000	20,858,000	17,254,000
Basic	$ (0.36)	$ 0.01	$ 1.53	$ 0.24	$ 2.47	$ 0.01	$ (1.87)	$ 3.03	$ 1.41	$ 3.50	$ 3.90
Diluted	$ (0.36)	$ 0.01	$ 1.44	$ 0.23	$ 2.33	$ 0.01	$ (1.87)	$ 2.86	$ 1.33	$ 3.29	$ 3.66
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									5,300	337	0
Stock Issued During Period, Shares, Acquisitions									3,200,000