Long-Term Debt (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Summary of long-term debt
Capital lease obligations related to real estate, maturing in varying amounts through November 2032 with a weighted average interest rate of 9.4%	$ 38,762	$ 39,295
Net carrying amount of liability component	510,361	497,264
Less current maturities of mortgage facility and other long-term debt	15,616	14,663
Long-Term Debt, net of current maturities	494,745	482,601
2.25% Convertible Senior Notes [Member]
Summary of long-term debt
Secured Long-Term Debt, Noncurrent	146,777	144,985
Net carrying amount of liability component	146,777	144,985
3.00% Convertible Senior Notes [Member]
Summary of long-term debt
Secured Long-Term Debt, Noncurrent	78,201	77,401
Net carrying amount of liability component	78,201	77,401
Mortgage Facility [Member]
Summary of long-term debt
Secured Debt	44,470	41,003
Other Real Estate Related Long-Term Debt [Member]
Summary of long-term debt
Other Real Estate Related and Long-Term Debt	$ 202,151	$ 194,580