Stock-Based Compensation - Nonvested Options (Details) - $ / shares	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Shares
Nonvested options at beginning of period (in shares)	3,307,210
Granted (in shares)	564,666	1,176,205	2,602,014
Vested (in shares)	(1,706,123)
Canceled/Forfeited (in shares)	(155,407)
Nonvested options at end of period (in shares)	2,010,346	3,307,210
Weighted Avg. Exercise Price
Nonvested options at beginning of period (in dollars per share)	$ 21.77
Granted (in dollars per share)	28.88	$ 23.17	$ 19.72
Vested (in dollars per share)	21.78
Canceled/Forfeited (in dollars per share)	23.71
Nonvested options at end of period (in dollars per share)	$ 23.61	$ 21.77