Financial Instruments and Fair Values - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) derivative	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) derivative	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	$ 31,227		$ 31,227		$ 1,922
Unrealized gain (loss) on valuation of swap agreement	930	$ (4,384)	(29,305)	$ (4,384)
Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	31,800		31,800
Designated as Hedging Instrument | Cash Flow Hedging
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain (loss) on valuation of swap agreement	$ 900		(29,300)
Loss expected to be reclassified within twelve months			$ 1,200
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		$ 465,000
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	$ 31,200		$ 31,200