Financial Instruments and Fair Values - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	$ (10,336,000)		$ (5,243,000)
Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	(10,400,000)
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount	515,000,000.0		515,000,000
Unrealized gain (loss) on valuation of interest rate swap agreements	(7,200,000)	$ 4,800,000
Amount expected to be reclassified within twelve months	(2,000,000)
Prepaid expenses and other assets | 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 asset			2,500,000
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	$ (10,300,000)		$ (5,200,000)