Income Taxes (Deferred Tax Assets and Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Deferred Tax Assets
Inventories	$ 25,874	$ 24,202
Accounts receivable	1,274	0
Deferred rental income	18,256	16,519
Insurance reserves	12,627	13,622
Litigation settlement and other reserves	3,181	3,856
Asset retirement obligations	7,180	6,463
Stock-based compensation	30,934	25,826
Other	20,590	19,694
Net operating loss carryforwards	13,081	16,419
Valuation allowance	(308)	(2,127)
Deferred tax assets, net	132,689	124,474
Deferred Tax Liabilities
Accounts receivable	0	(937)
Plant and equipment	(702,080)	(713,132)
Intangible assets	188,289	170,310
Other	(10,256)	(12,145)
Deferred tax liabilities	900,625	896,524
Net deferred tax liability	$ (767,936)	$ (772,050)