Debt (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Debt Instrument [Line Items]
Debt Instrument, Maturity year, start			Oct. 01, 2013		Jan. 01, 2013
Debt Instrument, Maturity year, end			Dec. 31, 2017		Dec. 31, 2017
Average borrowings outstanding	$ 449,800,000	$ 456,300,000	$ 477,500,000	$ 467,300,000
Weighted average interest rate of borrowings	7.00%	7.00%	7.00%	7.00%
Net interest expense incurred	8,600,000	8,100,000	25,600,000	24,400,000
Carrying value of debt instrument	397,790,000		397,790,000		397,479,000
7.25% Unsecured Notes due February 1, 2019 [Member]
Debt Instrument [Line Items]
Fair value of debt instrument	475,100,000		475,100,000		481,400,000
Carrying value of debt instrument	397,800,000		397,800,000		397,500,000
AUD $50 million portion of Revolver [Member]
Debt Instrument [Line Items]
Borrowings outstanding	46,589,000		46,589,000		51,915,000
USD $450 million portion of Revolver [Member]
Debt Instrument [Line Items]
Borrowings outstanding	$ 0		$ 0		$ 240,121,000
Other Indebtedness [Member]
Debt Instrument [Line Items]
Minimum interest rate			0.00%		0.00%
Maximum interest rate			6.00%		6.00%