Earnings Per Share (Computation of Basis and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator
Net income	$ 44,589	$ 33,252	$ 88,295	$ 67,177
Denominator
Denominator for basic earnings per share — weighted average shares outstanding (in shares)	50,330	50,455	50,297	51,073
Dilutive effect of nonvested restricted stock units and options issued to employees and directors (in shares)	331	356	375	353
Denominator for diluted earnings per share (in shares)	50,661	50,811	50,672	51,426
Earnings per Common Share:
Basic earnings per share (in USD per share)	$ 0.89	$ 0.66	$ 1.76	$ 1.32
Diluted earnings per share (in USD per share)	$ 0.88	$ 0.65	$ 1.74	$ 1.31