Condensed Consolidating Financial Information (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Feb. 28, 2012	Nov. 30, 2011	Jun. 30, 2011	Nov. 30, 2010
Condensed Consolidating Financial Information [Line Items]
Voting interest of the subsidiary owned by the registrant	100.00%
Eight Point Six Two Five Percent Senior Notes [Member]
Condensed Consolidating Financial Information [Line Items]
Senior Notes	$ 600,000	$ 600,000	$ 200,000	$ 200,000	$ 400,000	$ 400,000
Debt instrument interest rate	8.625%
Seven Point Five Percent Senior Notes [Member]
Condensed Consolidating Financial Information [Line Items]
Senior Notes	$ 300,000	$ 300,000
Debt instrument interest rate	7.50%