Income Tax Expense Unrecognized Tax Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2012
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Effective Income Tax Rate, Continuing Operations	31.80%	34.70%	32.50%	34.50%
Unrecognized Tax Benefits	$ 1,648		$ 1,648		$ 1,527
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	1,363		1,363		1,242
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Upper Bound	1,245		1,245
Income Tax Examination, Interest Accrued	1,062		1,062
Income Tax Examination, Penalties Accrued	$ 64		$ 64