Derivative Instruments And Hedging Activities - Narrative (Details) NOK in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2015 NOK	Sep. 30, 2013 USD ($)	Feb. 28, 2013 NOK	Feb. 28, 2013 USD ($)	Jan. 31, 2013 NOK	Jan. 31, 2013 USD ($)
Derivative [Line Items]
Losses in Accumulated OCI to be re-classified within twelve months			$ 9.8
Interest Rate Swaps [Member] | Term Loan Maturing June 2018 [Member]
Derivative [Line Items]
Notional amount						$ 148.1
Interest Rate Swaps [Member] | Nordea Q5000 Loan Maturing April 2020 [Member]
Derivative [Line Items]
Notional amount		$ 187.5		$ 187.5
Grand Canyon [Member]
Derivative [Line Items]
Notional amount									NOK 591.3	$ 104.6
Grand Canyon II [Member]
Derivative [Line Items]
Notional amount					NOK 434.1		NOK 594.7	$ 100.4
Grand Canyon I I I [Member]
Derivative [Line Items]
Notional amount					NOK 185.2		NOK 595.0	$ 98.8
Foreign Exchange Contracts For Grand Canyon And Grand Canyon III [Member] | Other Income (Expense), Net [Member]
Derivative [Line Items]
Unrealized gains (losses) on hedge ineffectiveness	$ 0.5		$ 0.1
Foreign Exchange Contracts For Grand Canyon II [Member] | Other Income (Expense), Net [Member]
Derivative [Line Items]
Realized losses on hedge ineffectiveness				0.2
Foreign Exchange Contracts For Grand Canyon III [Member] | Other Income (Expense), Net [Member]
Derivative [Line Items]
Unrealized gains (losses) on hedge ineffectiveness		$ 0.2		$ (3.2)