Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data	Sep. 30, 2011	Mar. 31, 2011
Condensed Consolidated Balance Sheets
Property and equipment, accumulated depreciation (in dollars)	$ 762,380	$ 740,773
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized shares	10,000	10,000
Preferred stock, issued shares	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares	175,000	300,000
Common stock, issued shares	46,508	39,508
Treasury stock, shares	1,880	2,370