Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Mar. 31, 2011
Condensed Consolidated Balance Sheets
Property and equipment, accumulated depreciation (in dollars)	$ 754,652	$ 740,773
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized shares	10,000,000	10,000,000
Preferred stock, issued shares	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares	300,000,000	300,000,000
Common stock, issued shares	46,508,000	39,508,000
Treasury stock, shares	2,361,000	2,370,000