Fair Value Measurements (Schedule of Carrying Values and Estimated Fair Values of Debt Instruments) (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Parent Company [Member]	Dec. 31, 2012 Parent Company [Member]	Feb. 14, 2011 2011 Notes [Member]	Jun. 30, 2013 2012 Notes [Member]	Oct. 25, 2012 2012 Notes [Member]	Jun. 30, 2013 8.25% Notes [Member]	Dec. 31, 2012 8.25% Notes [Member]	Jun. 30, 2013 Senior Credit Facility [Member]	Dec. 31, 2012 Senior Credit Facility [Member]
Debt Instrument [Line Items]
Interest Rate, Debt Instrument	8.25%							8.25%
Face amount of 8.25% Notes					$ 210,000,000	$ 300,000,000	$ 300,000,000	$ 510,000,000
Carrying Value	661,106,000	689,911,000	661,106,000	689,911,000				496,106,000	494,911,000	165,000,000	195,000,000
Estimated fair value	$ 690,300,000	$ 719,600,000						$ 525,300,000	$ 524,600,000	$ 165,000,000	$ 195,000,000