Derivative Instruments and Hedging Activities (Details) (USD $)	12 Months Ended							12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Interest Expense [Member]	Dec. 31, 2011 Interest Expense [Member]	Dec. 31, 2012 Cash flow hedges [Member] Interest Expense [Member]	Dec. 31, 2012 Interest Rate Swap [Member]	Sep. 30, 2012 Interest Rate Swap [Member]	Aug. 31, 2010 Interest Rate Swap [Member]	Dec. 31, 2012 Interest Rate Swap [Member] Cash flow hedges [Member]	Dec. 31, 2012 Designated as Hedging Instrument [Member] Interest Rate Swap [Member]	Dec. 31, 2011 Designated as Hedging Instrument [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Designated as Hedging Instrument [Member] Accrued liabilities and other [Member] Interest Rate Swap [Member]	Dec. 31, 2011 Designated as Hedging Instrument [Member] Accrued liabilities and other [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Designated as Hedging Instrument [Member] Deferred charges and other assets, net [Member] Interest Rate Swap [Member]	Dec. 31, 2011 Designated as Hedging Instrument [Member] Deferred charges and other assets, net [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Interest Rate Swap [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Accrued liabilities and other [Member] Interest Rate Swap [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] Accrued liabilities and other [Member] Interest Rate Swap [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Other liabilities [Member] Interest Rate Swap [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] Other liabilities [Member] Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities [Abstract]
Notional amount of interest rate swaps not designated as cash flow hedges	$ 52,200,000
Notional amount of cash flow hedges	174,600,000
Derivatives, Fair Value [Line Items]
Derivative, expiry date	Jul. 31, 2013				Jul. 31, 2013
Amount of notional principal interest rate swap						174,600,000	63,300,000
Derivatives Liabilities, Fair Value											1,613,000	0					239,000	331,000	0	121,000
Derivative Assets, Fair Value													177,000	0
Derivative Assets (Liabilities), at Fair Value, Net									1,436,000	0					239,000	452,000
Derivative Instruments, Gain (Loss) [Line Items]
Changes in fair value recorded in interest expense		213,000	410,000
Amount reclassified as an increase to interest expense during next twelve months		1,600,000
Amount of Gain or (Loss) Recognized in Other Comprehensive Income on Derivative (Effective Portion)								(1,436,000)
Amount of Gain or (Loss) Reclassified from Accumulated Other Comprehensive Income into Income (Effective Portion)				$ 481,000