Derivative Instruments and Hedging Activities - Open Interest Rate Swap Contracts (Details) - Cash Flow Hedging - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Interest Rate Swap, May 2018 To May 2021 [Member]
Derivative [Line Items]
Notional Amounts (in U.S. dollars)	$ 25,000	$ 0
Net Unrealized Gain (Loss)	397	0
Interest Rate Swap, September 2018 To September 2019 [Member]
Derivative [Line Items]
Notional Amounts (in U.S. dollars)	250,000	0
Net Unrealized Gain (Loss)	(163)	0
Interest Rate Swap, September 2019 To September 2023 [Member]
Derivative [Line Items]
Notional Amounts (in U.S. dollars)	150,000	0
Net Unrealized Gain (Loss)	(2,899)	0
Interest Rate Swap
Derivative [Line Items]
Notional Amounts (in U.S. dollars)	425,000	0
Net Unrealized Gain (Loss)	$ (2,665)	$ 0