Derivative Instruments and Hedging Activities - Offsetting Assets and Liabilities (Details) - Pro Forma - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative assets
Gross Amounts of Recognized Assets/ Liabilities	$ 1,957	$ 1,639
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets/ Liabilities Presented in the Consolidated Balance Sheet	1,957	1,639
Gross Amounts Not Offset in the Consolidated Balance Sheet
Derivative Financial Instruments	(457)	(875)
Cash Collateral Received (Pledged)	0	0
Net Amount	1,500	764
Derivative liabilities
Gross Amounts of Recognized Assets/ Liabilities	(457)	(875)
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets/ Liabilities Presented in the Consolidated Balance Sheet	(457)	(875)
Gross Amounts Not Offset in the Consolidated Balance Sheet
Derivative Financial Instruments	457	875
Cash Collateral Received (Pledged)	0	0
Net Amount	$ 0	$ 0