Financial Instruments and Fair Values - Narrative (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) derivative	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) derivative	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	$ 32,157,000		$ 32,157,000		$ 1,922,000
Unrealized loss on valuation of swap agreement	10,864,000	$ 0	30,235,000	$ 0
Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	33,100,000		33,100,000
Designated as Hedging Instrument | Cash Flow Hedging
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized loss on valuation of swap agreement	$ 10,900,000		30,200,000
Gain (loss) expected to be reclassified within twelve months			$ 0
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, number of instruments held (derivative) | derivative	3		3
Notional amount	$ 465,000,000		$ 465,000,000
Accounts payable and accrued expenses | Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	$ 32,200,000		$ 32,200,000