Earnings per Share Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Income (Loss) Attributable to Parent	$ 73,537	$ 37,838	$ 159,791	$ 85,807
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Weighted Average Number of Shares Outstanding, Basic	28,653	27,981	28,554	27,695
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Incremental Common Shares Attributable to Stock Options	376	403	253	338
Deferred Compensation Awards	257	214	223	205
Diluted Weighted Average Number of Shares Outstanding	29,286	28,598	29,030	28,238
Earnings Per Share, Basic	$ 2.57	$ 1.35	$ 5.60	$ 3.10
Earnings Per Share, Diluted	$ 2.51	$ 1.32	$ 5.50	$ 3.04
Anti-dilutive stock equivalent awards not included in the calculation of diluted loss per share	435	0	360	412