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, 2018	Dec. 31, 2017
Derivatives Designated as Hedging Instruments | Other Assets
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 135	$ 18
Derivatives Designated as Hedging Instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Liability Derivatives	688	1,383
Derivatives Not Designated as Hedging Instruments | Other Assets
Derivatives, Fair Value [Line Items]
Asset Derivatives	11,948	7,305
Derivatives Not Designated as Hedging Instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ 11,948	$ 7,305