Fair Value of Assets and Liabilities (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2011	Jan. 03, 2011	Dec. 31, 2010
Fair Value of Assets and Liabilities
Interest rate stated percentage (as a percent)	1.53%
Convertible senior notes, due 2027 at 3.8% | Carrying Amount
Fair Value of Assets and Liabilities
Financial liabilities	79,054		79,054
Mortgage note, due 2011 at 8.3% | Carrying Amount
Fair Value of Assets and Liabilities
Financial liabilities			3,383
Carrying Amount
Fair Value of Assets and Liabilities
Unamortized discounts	(5,895)		(8,043)
Total financial liabilities	1,965,988		1,967,223
Carrying Amount | Senior Notes, due 2012 at 6.85%
Fair Value of Assets and Liabilities
Financial liabilities	100,829		100,829
Carrying Amount | Senior Notes, due 2013 at 6.75%
Fair Value of Assets and Liabilities
Financial liabilities	287,000		287,000
Carrying Amount | Senior Notes, due 2014 at 7.875%
Fair Value of Assets and Liabilities
Financial liabilities	300,000		300,000
Carrying Amount | Senior Notes, due 2015 at 5.125%
Fair Value of Assets and Liabilities
Financial liabilities	280,000		280,000
Carrying Amount | Senior Notes, due 2016 at 6.3%
Fair Value of Assets and Liabilities
Financial liabilities	275,000		275,000
Carrying Amount | Senior Notes, due 2017 at 5.625%
Fair Value of Assets and Liabilities
Financial liabilities	300,000		300,000
Carrying Amount | Senior Notes, due 2018 at 6.7%
Fair Value of Assets and Liabilities
Financial liabilities	350,000		350,000
Convertible senior notes, due 2027 at 3.8% | Fair Value
Fair Value of Assets and Liabilities
Financial liabilities	79,645		81,579
Mortgage note, due 2011 at 8.3% | Fair Value
Fair Value of Assets and Liabilities
Financial liabilities			3,408
Fair Value
Fair Value of Assets and Liabilities
Total financial liabilities	2,114,271		2,163,948
Fair Value | Senior Notes, due 2012 at 6.85%
Fair Value of Assets and Liabilities
Financial liabilities	104,702		109,897
Fair Value | Senior Notes, due 2013 at 6.75%
Fair Value of Assets and Liabilities
Financial liabilities	300,620		315,364
Fair Value | Senior Notes, due 2014 at 7.875%
Fair Value of Assets and Liabilities
Financial liabilities	334,101		349,974
Fair Value | Senior Notes, due 2015 at 5.125%
Fair Value of Assets and Liabilities
Financial liabilities	290,409		296,782
Fair Value | Senior Notes, due 2016 at 6.3%
Fair Value of Assets and Liabilities
Financial liabilities	301,001		297,795
Fair Value | Senior Notes, due 2017 at 5.625%
Fair Value of Assets and Liabilities
Financial liabilities	314,425		316,846
Fair Value | Senior Notes, due 2018 at 6.7%
Fair Value of Assets and Liabilities
Financial liabilities	389,368		392,303
Mortgage note, due 2011 at 8.3%
Fair Value of Assets and Liabilities
Interest rate stated percentage (as a percent)	8.30%	8.30%	8.30%
Senior Notes, due 2012 at 6.85%
Fair Value of Assets and Liabilities
Interest rate stated percentage (as a percent)	6.85%		6.85%
Senior Notes, due 2013 at 6.75%
Fair Value of Assets and Liabilities
Interest rate stated percentage (as a percent)	6.75%		6.75%
Senior Notes, due 2014 at 7.875%
Fair Value of Assets and Liabilities
Interest rate stated percentage (as a percent)	7.875%		7.875%
Senior Notes, due 2015 at 5.125%
Fair Value of Assets and Liabilities
Interest rate stated percentage (as a percent)	5.125%		5.125%
Senior Notes, due 2016 at 6.3%
Fair Value of Assets and Liabilities
Interest rate stated percentage (as a percent)	6.30%		6.30%
Senior Notes, due 2017 at 5.625%
Fair Value of Assets and Liabilities
Interest rate stated percentage (as a percent)	5.625%		5.625%
Senior Notes, due 2018 at 6.7%
Fair Value of Assets and Liabilities
Interest rate stated percentage (as a percent)	6.70%		6.70%
Convertible senior notes, due 2027 at 3.8%
Fair Value of Assets and Liabilities
Unamortized discounts	(574)		(1,570)
Total financial liabilities	78,480		77,484
Interest rate stated percentage (as a percent)	3.80%		3.80%