General and Summary of Significant Accounting Policies Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Diluted	$ 0.54	$ 1.09	$ 0.98	$ 0.96	$ 0.33	$ 0.98	$ 0.83	$ 0.60	$ 3.66	$ 2.73	$ 1.68
Net Income	$ 9,512	$ 18,806	$ 16,606		$ 5,463	$ 16,266	$ 13,570	$ 9,686	$ 63,084	$ 44,985	$ 26,335
Basic	$ 0.58	$ 1.16	$ 1.03	0.99	$ 0.34	$ 1.02	$ 0.86	$ 0.62	$ 3.90	$ 2.84	$ 1.72
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options									$ 7,556	$ 9,330	$ 5,700
Adjustments for New Accounting Pronouncement [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Diluted				$ 1.08
Net Income				$ 18,160
Basic				$ 1.13
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options				$ 2,300