Derivative Instruments, Hedging Activities and Accumulated Other Comprehensive Income (Details) (USD $)	3 Months Ended															3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Gains and Losses on Cash Flow Hedges [Member]	Mar. 31, 2013 Interest Rate Swap [Member]	Sep. 30, 2012 Interest Rate Swap [Member]	Aug. 31, 2010 Interest Rate Swap [Member]	Mar. 31, 2013 Designated as Hedging Instrument [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Designated as Hedging Instrument [Member] Interest Rate Swap [Member]	Mar. 31, 2013 Designated as Hedging Instrument [Member] Accrued liabilities and other [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Designated as Hedging Instrument [Member] Accrued liabilities and other [Member] Interest Rate Swap [Member]	Mar. 31, 2013 Designated as Hedging Instrument [Member] Deferred charges and other assets, net [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Designated as Hedging Instrument [Member] Deferred charges and other assets, net [Member] Interest Rate Swap [Member]	Mar. 31, 2013 Not Designated as Hedging Instrument [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Interest Rate Swap [Member]	Mar. 31, 2013 Not Designated as Hedging Instrument [Member] Accrued liabilities and other [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Accrued liabilities and other [Member] Interest Rate Swap [Member]	Mar. 31, 2013 Interest Expense [Member]	Mar. 31, 2012 Interest Expense [Member]
Derivative Instruments, Hedging Activities and Accumulated Other Comprehensive Income [Abstract]
Notional amount of interest rate swaps not designated as cash flow hedges	$ 50,600,000
Notional amount of cash flow hedges	174,600,000
Derivative Instruments, Gain (Loss) [Line Items]
Changes in fair value recorded in interest expense																(104,000)	28,000
Amount reclassified as an increase to interest expense during next twelve months																1,600,000
Derivatives, Fair Value [Line Items]
Amount of notional principal interest rate swap				174,600,000	63,300,000
Derivative, expiry date	Jul. 31, 2013		Jul. 31, 2013
Derivatives Liabilities, Fair Value								1,559,000	1,613,000					135,000	239,000
Derivative Assets, Fair Value										1,007,000	177,000
Derivative Assets (Liabilities), at Fair Value, Net						552,000	1,436,000					135,000	239,000
Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), before Tax		(1,436,000)
Other comprehensive income before reclassifications, before tax		490,000
Amounts reclassified from accumulated other comprehensive income (to interest expense), before tax		394,000
Net current period other comprehensive income before tax		884,000
Accumulated Other Comprehensive Income (Loss), before Tax		(552,000)
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Tax		573,000
Other comprehensive income before reclassifications, tax		(196,000)
Amounts reclassified From accumulated other comprehensive income tax (to interest expense)		(156,000)
Net current period other comprehensive income, tax		(352,000)
Accumulated Other Comprehensive Income (Loss), Tax		221,000
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Total	(863,000)	(863,000)
Other comprehensive income before reclassifications, net of tax		294,000
Amounts reclassified from accumulated other comprehensive income (to interest expense), net of tax		238,000
Net current period other comprehensive income, net of tax		532,000
Accumulated Other Comprehensive Income (Loss), Net of Tax, Total	$ (331,000)	$ (331,000)