Long-term Debt - 7.50% Senior Notes (Details) (USD $)		6 Months Ended						6 Months Ended	0 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Debt Instrument, Redemption, Period One [Member]	Jun. 30, 2013 Debt Instrument, Redemption, Period Two [Member]	Jun. 30, 2013 Debt Instrument, Redemption, Period Three [Member]	Jun. 30, 2013 Debt Instrument, Redemption, Period Four [Member]	Jun. 30, 2013 Senior Notes [Member]	Mar. 02, 2013 Senior Notes [Member]	Jun. 30, 2013 Senior Notes [Member] Prior to March 1 2016 [Member]	Mar. 02, 2013 Senior Notes [Member] Change in Control [Member]
Debt Instrument [Line Items]
Long-term debt, principal amount							$ 500,000,000
Debt instrument, stated interest rate (percent)	7.50%					7.50%	7.50%
Debt Instrument, Debt Redemption, Redeemable Principal Amount, Percentage								35.00%
Debt Instrument, Debt Redemption Rates, Percentage of Principal		105.625%	103.75%	101.875%	100.00%
Redemption Price of Debt Instrument, Principal, Percentage									101.00%