Debt Interest Expense and Other Debt Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Debt Instrument [Line Items]
Interest Expense, Debt	$ 36,850,000		$ 34,456,000		$ 22,509,000
Interest Costs, Capitalized During Period	891,000		455,000		1,008,000
Interest Expense	35,959,000		34,001,000		21,501,000
Interest Paid	34,825,000	[1]	31,305,000	[1]	21,721,000	[1]
Partial Settlement of Interest Rate Swap-Cash Flow Hedge [Member]
Debt Instrument [Line Items]
Interest Expense, Debt	0		1,076,000		0
Fair Value Adjustments on Hedges and Derivative Contracts [Member]
Debt Instrument [Line Items]
Interest Expense, Debt	41,000	[2]	1,464,000	[2]	175,000	[2]
Net amortization discount and deferred debt issuance costs [Member]
Debt Instrument [Line Items]
Interest Expense, Debt	1,212,000		713,000		706,000
Commitment Fees [Member]
Debt Instrument [Line Items]
Interest Expense, Debt	430,000		392,000		268,000
Long-term Debt [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Interest Expense, Debt	10,477,000		9,109,000		10,657,000
Long-term Debt [Member] | Senior Notes [Member] | 6.25% Interest Rate [Member]
Debt Instrument [Line Items]
Interest Expense, Debt	11,565,000		11,404,000		10,703,000
Long-term Debt [Member] | Senior Notes [Member] | 8.25% Interest Rate [Member]
Debt Instrument [Line Items]
Interest Expense, Debt	12,380,000		10,298,000		0
Long-term Debt [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Interest Expense, Debt	745,000		0		0
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Notional Amount of Interest Rate Derivatives			$ 1,900,000		$ 3,800,000

[1] Presented net of cash received under previous interest rate swap contracts of $1.9 million and $3.8 million for the years ended December 31, 2010 and 2009, respectively.

[2] Includes fair value adjustments to previous interest rate swap contracts settled during the first quarter of 2010.