Stockholders' Equity (Change in Retained Earnings) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			$ 798,370
Net income	$ 156,921	$ 156,706	145,971	$ 160,374
Repurchase of common stock			(69,190)
Balance, end of period	$ 875,151		$ 875,151