Derivative Instruments and Hedging Activities - Fair Value of Derivative Financial Instruments and Their Classification on Balance Sheet (Details) - Interest Rate Contracts - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives Designated as Hedging Instruments | Other Assets
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 18	$ 15
Derivatives Designated as Hedging Instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Liability Derivatives	1,383	2,182
Derivatives Not Designated as Hedging Instruments | Other Assets
Derivatives, Fair Value [Line Items]
Asset Derivatives	7,305	6,295
Derivatives Not Designated as Hedging Instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ 7,305	$ 6,295