Fair Value Measurements Fair Value Measurements (Details Textual 2) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013
Debt Instrument [Line Items]
Impairment of Long-Lived Assets Held-for-use	$ 0	$ 0
Fair Value Measurements, Changes in Valuation Techniques	0	0
Senior Notes Six Point Zero Percent Due Twenty Thirteen [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.00%	6.00%
Senior Notes Six Point Eight Seven Five Percent Due Twenty Eighteen [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.875%	6.875%