EARNINGS PER SHARE AND STOCKHOLDERS' EQUITY: Narrative (Details) - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Antidilutive securities excluded from computation of earnings per share, amount	97	156	89	345
Repurchase of stock (in shares)	1,600		1,600
Payments for repurchase of common stock			$ 39,441,000	$ 30,542,000
Treasury stock, at cost	$ 1,088,988,000		1,088,988,000		$ 1,039,345,000
Accumulated other comprehensive income	9,826,000		9,826,000		$ 7,999,000
Common Stock Repurchase Program
Stock repurchase program, authorized amount	$ 400,000,000		$ 400,000,000
Repurchase of stock (in shares)	18,400		18,400
Treasury stock, at cost	$ 325,200,000		$ 325,200,000
Stock repurchase program, remaining amount	$ 74,800,000		$ 74,800,000