Indebtedness (Schedule of Indebtedness) (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
8.25% Senior Notes, face amount of $510.0 million, interest rate of 8.25% payable semi-annually, in arrears on February 15 and August 15 of each year, maturity date February 15, 2018	$ 496,723,000	$ 494,911,000
Senior Credit Facility, interest rate based on base rate or LIBOR plus a floating spread, maturity date October 31, 2016	125,000,000	195,000,000
Total indedtedness	621,723,000	689,911,000
Current portion of indebtedness	0	0
Noncurrent portion of indebtedness	621,723,000	689,911,000
Interest Rate, Debt Instrument	8.25%
2012 Notes [Member]
Senior Notes, face amount	300,000,000
8.25% Notes [Member]
Noncurrent portion of indebtedness	496,723,000	494,911,000
Senior Notes, face amount	510,000,000
Interest Rate, Debt Instrument	8.25%
Maturity date	Feb. 15, 2018
Parent Company [Member]
Noncurrent portion of indebtedness	621,723,000	689,911,000
Senior Credit Facility [Member]
Noncurrent portion of indebtedness	$ 125,000,000	$ 195,000,000
Maturity date	Oct. 31, 2016