Earnings per Share Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income	$ 239,874	$ 127,587	$ 107,663
Diluted income available to common shareholders	$ 239,874	$ 127,587	$ 108,070
Basic Weighted Average Shares Outstanding	28,610	27,846	28,234
Stock option awards	298	412	295
Deferred Compensation Awards	244	217	219
Diluted Weighted Average Shares Outstanding	29,152	28,475	29,178
Earnings Per Share, Basic	$ 8.38	$ 4.58	$ 3.81
Earnings Per Share, Diluted	$ 8.23	$ 4.48	$ 3.70
Anti-dilutive stock equivalent awards not included in the calculation of diluted loss per share	379	1	381
2018 Convertible Senior Notes [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Interest on convertible senior subordinated notes	$ 0	$ 0	$ 407
Convertible senior subordinated notes potential shares	0	0	430