Income Taxes (Components of Income Tax Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Current [Abstract]
Federal		$ 145,603	$ 94,665	$ 77,466
Foreign		7,042	2,758	2,317
State		13,589	12,817	7,246
Total current income tax expense		166,234	110,240	87,029
Deferred [Abstract]
Federal		26,993	65,456	56,506
Foreign		(975)	474	33
State		10,291	2,622	13,101
Total deferred income tax expense		36,309	68,552	69,640
Income tax expense	$ (4,900)	$ 202,543	$ 178,792	$ 156,669