Long-Term Debt (Details 8) (USD $)	Dec. 31, 2013	Dec. 31, 2013 4.25% convertible senior notes due June 2014	Dec. 31, 2012 4.25% convertible senior notes due June 2014	Jun. 30, 2009 4.25% convertible senior notes due June 2014	Dec. 31, 2013 Partnership's 6% notes due 2021	Mar. 31, 2013 Partnership's 6% notes due 2021
Long-Term Debt Maturity Schedule
2014	$ 355,000,000
2015	427,000
2016	49,234,000
2017	234,000
2018	763,234,000
Thereafter	350,410,000
Total Long-Term Debt	1,518,539,000
Long-Term Debt
Interest rate (as a percent)		4.25%	4.25%	4.25%	6.00%
Amount of unamortized discount of notes		$ 11,300,000	$ 34,300,000	$ 97,900,000	$ 5,000,000	$ 5,500,000