Indebtedness (Revolving Credit Agreement) (Details) (USD $)	12 Months Ended							0 Months Ended
	Mar. 31, 2014 Revolving credit agreement	Mar. 31, 2013 Revolving credit agreement	Mar. 31, 2012 Revolving credit agreement	Mar. 23, 2012 Revolving credit agreement	Mar. 23, 2012 Swing-line loans [Member]	Mar. 31, 2014 Letters of credit [Member]	Mar. 23, 2012 Letters of credit [Member]	Mar. 23, 2012 London Interbank Offered Rate (LIBOR) [Member] Revolving credit agreement Minimum [Member]	Mar. 23, 2012 London Interbank Offered Rate (LIBOR) [Member] Revolving credit agreement Maximum [Member]	Mar. 23, 2012 Weighted-average Overnight Federal Fund Rates [Member] Revolving credit agreement Fixed component [Member]	Mar. 23, 2012 Weighted-average Overnight Federal Fund Rates [Member] Revolving credit agreement Variable component [Member] Minimum [Member]	Mar. 23, 2012 Weighted-average Overnight Federal Fund Rates [Member] Revolving credit agreement Variable component [Member] Maximum [Member]
Revolving Credit Agreement [Line Items]
Maximum borrowing capacity				$ 400,000,000	$ 25,000,000		$ 25,000,000
Additional borrowing capacity with the approval of the lenders				100,000,000
Basis spread on variable rate								0.875%	1.75%	0.50%	0.00%	0.75%
Maximum amount outstanding	208,730,000	220,470,000	216,180,000
Weighted-average amount outstanding	190,015,000	203,072,000	194,055,000
Weighted-average interest rate	1.50%	1.50%	1.10%
Amount outstanding						4,050,000
Unused commitments	$ 235,595,000