Derivatives - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2015	Jan. 31, 2014
Derivative [Line Items]
Settlement Gain on Derivative Instruments	$ 0	$ 1,896	$ 0
2018 Treasury Locks
Derivative [Line Items]
Debt instrument, LIBOR Rate	ten year U.S. Treasury
Swaps, Number of Instruments Held	2
Swaps, Notional Amount	$ 100,000
Swaps, Average Fixed Interest Rate	2.93%
2014 Swaps
Derivative [Line Items]
Debt instrument, LIBOR Rate	one month LIBOR
Swaps, Number of Instruments Held						4
Swaps, Notional Amount						$ 200,000
Swaps, Average Fixed Interest Rate						2.29%
2015 Swaps
Derivative [Line Items]
Debt instrument, LIBOR Rate	one month LIBOR
Swaps, Number of Instruments Held					6
Swaps, Notional Amount					$ 260,000
Swaps, Average Fixed Interest Rate					1.79%
2017 Treasury Locks
Derivative [Line Items]
Debt instrument, LIBOR Rate		ten year U.S. Treasury
Swaps, Number of Instruments Held				2
Swaps, Notional Amount				$ 100,000
Swaps, Average Fixed Interest Rate				2.18%
Settlement Gain on Derivative Instruments		$ 1,896