Equity Compensation (Summary of Outstanding and Exercisable Options) (Details) shares in Thousands	12 Months Ended
	Mar. 31, 2018 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number (in shares) | shares	1,740
Options Outstanding, Weighted Average Remaining Contractual Life	6 years 1 month 10 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 31.91
Options Exercisable, Number Exercisable (in shares) | shares	1,182
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 25.20
$2.90 - $16.25
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	2.90
Range of Exercise Prices, upper limit	$ 16.25
Options Outstanding, Number (in shares) | shares	403
Options Outstanding, Weighted Average Remaining Contractual Life	2 years 6 months 30 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 13.09
Options Exercisable, Number Exercisable (in shares) | shares	403
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 13.09
$16.28 - $23.34
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	16.28
Range of Exercise Prices, upper limit	$ 23.34
Options Outstanding, Number (in shares) | shares	354
Options Outstanding, Weighted Average Remaining Contractual Life	5 years 10 months 14 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 21.78
Options Exercisable, Number Exercisable (in shares) | shares	320
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 21.91
$23.80 - $23.80
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	23.80
Range of Exercise Prices, upper limit	$ 23.80
Options Outstanding, Number (in shares) | shares	3
Options Outstanding, Weighted Average Remaining Contractual Life	5 years 5 months 5 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 23.80
Options Exercisable, Number Exercisable (in shares) | shares	3
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 23.80
$31.25 - $31.25
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	31.25
Range of Exercise Prices, upper limit	$ 31.25
Options Outstanding, Number (in shares) | shares	321
Options Outstanding, Weighted Average Remaining Contractual Life	7 years 7 months 6 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 31.25
Options Exercisable, Number Exercisable (in shares) | shares	170
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 31.25
$32.29 - $54.65
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	32.29
Range of Exercise Prices, upper limit	$ 54.65
Options Outstanding, Number (in shares) | shares	443
Options Outstanding, Weighted Average Remaining Contractual Life	6 years 8 months 27 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 46.06
Options Exercisable, Number Exercisable (in shares) | shares	286
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 42.37
$55.72 - $55.72
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, lower limit	55.72
Range of Exercise Prices, upper limit	$ 55.72
Options Outstanding, Number (in shares) | shares	216
Options Outstanding, Weighted Average Remaining Contractual Life	9 years 7 months 2 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 55.72
Options Exercisable, Number Exercisable (in shares) | shares	0
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 0.00