Derivative Instruments, Hedging Activities and Accumulated Other Comprehensive Income (Details) (USD $)			6 Months Ended	3 Months Ended									3 Months Ended	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Gains and (Losses) on Cash Flow Hedges [Member]	Jun. 30, 2013 Interest Rate Swaps [Member]	Sep. 30, 2012 Interest Rate Swaps [Member]	Aug. 31, 2010 Interest Rate Swaps [Member]	Jun. 30, 2014 Designated as Hedging Instrument [Member] Interest Rate Swaps [Member]	Dec. 31, 2013 Designated as Hedging Instrument [Member] Interest Rate Swaps [Member]	Jun. 30, 2014 Designated as Hedging Instrument [Member] Accrued liabilities and other [Member] Interest Rate Swaps [Member]	Dec. 31, 2013 Designated as Hedging Instrument [Member] Accrued liabilities and other [Member] Interest Rate Swaps [Member]	Jun. 30, 2014 Designated as Hedging Instrument [Member] Deferred charges, and other assets net [Member] Interest Rate Swaps [Member]	Dec. 31, 2013 Designated as Hedging Instrument [Member] Deferred charges, and other assets net [Member] Interest Rate Swaps [Member]	Jun. 30, 2013 Interest Expense [Member]	Jun. 30, 2014 Interest Expense [Member]
Derivative Instruments, Hedging Activities and Accumulated Other Comprehensive Income [Abstract]
Notional amount of cash flow hedges	$ 174,600,000
Derivative Instruments, Gain (Loss) [Line Items]
Changes in fair value recorded in interest expense													102,000
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
Derivatives Liabilities, Fair Value									1,613,000	1,590,000
Derivative Assets, Fair Value											(3,846,000)	(5,926,000)
Derivative Assets (Liabilities), at Fair Value, Net							(2,233,000)	(4,336,000)
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), before Tax			4,336,000
Other comprehensive income before reclassifications, before tax			(2,957,000)
Amounts reclassified from accumulated other comprehensive income (to interest expense), before tax			854,000
Net current period other comprehensive income (loss), before tax			(2,103,000)
Accumulated Other Comprehensive Income (Loss), before Tax			2,233,000
Accumulated Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), tax			(1,742,000)
Other comprehensive income before reclassifications, tax			1,184,000
Amounts reclassified From accumulated other comprehensive income (to interest expense), tax			(341,000)
Net current period other comprehensive income (loss), tax			843,000
Accumulated Other Comprehensive Income (Loss), tax			(899,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), net of tax	1,334,000	2,594,000	2,594,000
Other comprehensive income before reclassifications, net of tax			(1,773,000)
Amounts reclassified from accumulated other comprehensive income (to interest expense), net of tax			513,000
Net current period other comprehensive income (loss), net of tax			(1,260,000)
Accumulated Other Comprehensive Income (Loss), net of tax	$ 1,334,000	$ 2,594,000	$ 1,334,000