Derivative Financial Instruments (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Gain on forward starting interest rate swaps	$ 4,161,000	$ 1,732,000	$ 5,703,000
Expected decrease to interest expense	1,600,000
Derivatives designated as cash flow hedges in prepaid expenses and other assets [Abstract]
Interest rate swaps	1,146,000	1,286,000
Derivatives designated as cash flow hedges in accounts payable, accrued expenses and other liabilities [Abstract]
Interest rate swaps	3,581,000	0
Amount of unrealized gains recognized in accumulated other comprehensive income/(loss) on derivatives (effective portion) [Abstract]
Interest rate swaps	4,161,000	1,732,000	5,703,000
Amount of (gains)/losses reclassified out of accumulated other comprehensive income/(loss) into contractual interest expense (effective portion) [Abstract]
Interest rate swaps	(2,086,000)	1,157,000	3,057,000
Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Amount of borrowings outstanding, subject to swaps	$ 225,000,000.0	$ 150,000,000	$ 150,000,000
Underlying treasury rate term (in years)	10 years	10 years	10 years
Weighted average interest rate under derivative instruments (in hundredths)	2.86%	2.44%	1.90%
Gain on forward starting interest rate swaps	$ 7,000,000	$ 7,300,000
Gain on hedge ineffectiveness in interest expense	200,000
Amount of unrealized gains recognized in accumulated other comprehensive income/(loss) on derivatives (effective portion) [Abstract]
Interest rate swaps	7,000,000	7,300,000
Floating to Fixed Interest Rate Swaps (2017) [Member]
Derivatives, Fair Value [Line Items]
Amount of borrowings outstanding, subject to swaps		$ 50,000,000
Underlying treasury rate term (in years)		1 month
Derivative maturity date		Jan. 31, 2022
Floating to Fixed Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Amount of borrowings outstanding, subject to swaps	$ 225,000,000
Derivative maturity date	Jan. 11, 2019
Weighted average interest rate under derivative instruments (in hundredths)	1.678%
4.125% (4.271% effective rate) Notes due 2028 [Member]
Derivatives, Fair Value [Line Items]
Principal amount of debt	$ 350,000,000
Stated interest rate (in hundredths)	4.125%
3.875% (4.038% effective rate) Notes due 2027 [Member]
Derivatives, Fair Value [Line Items]
Principal amount of debt		$ 300,000,000
Stated interest rate (in hundredths)		3.875%
London Interbank Offered Rate (LIBOR) [Member] | Floating to Fixed Interest Rate Swaps (2017) [Member]
Derivatives, Fair Value [Line Items]
Weighted average interest rate under derivative instruments (in hundredths)		1.693%