Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator
Net income	$ 117,910	$ 38,450	$ 219,562	$ 64,576
Denominator
Weighted average common shares outstanding - basic	33,738,586	33,340,184	33,651,727	33,274,056
Dilutive effect of restricted stock units	218,052	121,510	269,212	195,013
Weighted average common shares outstanding - diluted	33,956,638	33,461,694	33,920,939	33,469,069
Earnings per share:
Basic	$ 3.49	$ 1.15	$ 6.52	$ 1.94
Diluted	$ 3.47	$ 1.15	$ 6.47	$ 1.93