Income Taxes (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	$ 328,874,000	[1],[2]	$ 509,485,000	[1],[2]
Payments for income taxes, net of tax refunds received	12,400,000		32,300,000		22,300,000
Unrecognized Tax Benefits	21,200,000
Tunisia and South Africa [Member]
Operating Loss Carryforwards [Line Items]
Payments for income taxes, net of tax refunds received			9,800,000		12,200,000
UNITED STATES
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	917,400,000
COLORADO
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	122,000,000
KANSAS
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	32,000,000
Deferred Tax Assets, Operating Loss Carryforwards	50,600,000
Deferred Tax Assets, Valuation Allowance	$ 1,500,000

[1] Net operating loss carryforwards as of December 31, 2013 consist of $917.4 million of U.S. federal NOLs which expire primarily in 2032, $122.0 million of Colorado NOLs which expire between 2027 and 2033 and $50.6 million of Kansas NOLs which expire between 2018 and 2023.

[2] Net operating loss carryforwards as of December 31, 2013 are net of a $1.5 million valuation allowance relating to $32 million of Kansas NOLs that the Company believes will more likely than not expire unutilized.