Derivative Financial Instruments and Hedging Activities - Derivative Offsetting (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Offsetting of Derivative Assets
Asset Derivatives	$ 1,999	$ 1,529
Gross Amounts in the Consolidated Balance Sheets	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	1,999	1,529
Financial Instruments	0	0
Cash Collateral Received	0	0
Net Amount	1,999	1,529
Offsetting of Derivative Liabilities
Liability Derivatives	548	1,089
Gross Amounts in the Consolidated Balance Sheets	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets	548	1,089
Financial Instruments	0	0
Cash Collateral Received	0	0
Net Amount	$ 548	$ 1,089