Derivative Instruments and Hedge Activities - Summary of Net Gains (Losses) Recorded in Accumulated Other Comprehensive Income (Loss) and Consolidated Statements of Operations Relating to Cash Flow Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Unrealized holding gains (losses) arising during the period	$ 1,070	$ 17	$ 6,702	$ (1,408)
Interest Rate Swaps
Derivative [Line Items]
Unrealized holding gains (losses) arising during the period			6,702	(1,408)
Amount of Gain (Loss) Reclassified from OCI to Income as a Decrease to Interest Expense			$ 863	$ (426)