Derivative Instruments and Hedging Activities - Interest Rate Swaps Floating Rate Payments Exchanged for Fixed Rate Payments (Details) - Cash Flow Hedging - Designated as Hedging Instrument - Interest rate swaps - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Notional Amount	$ 495,500,000	$ 345,500,000
Weighted Average Fixed Pay Interest Rate	2.60%	2.33%
Weighted Average Variable Interest Rate	2.52%	1.38%
Swap Maturity, 2024
Derivative [Line Items]
Notional Amount	$ 98,000,000	$ 98,000,000
Weighted Average Fixed Pay Interest Rate	2.18%	2.18%
Weighted Average Variable Interest Rate	2.45%	1.36%
Swap Maturity, 2027
Derivative [Line Items]
Notional Amount	$ 247,500,000	$ 247,500,000
Weighted Average Fixed Pay Interest Rate	2.39%	2.39%
Weighted Average Variable Interest Rate	2.53%	1.39%
Swap Maturity, 2028
Derivative [Line Items]
Notional Amount	$ 150,000,000	$ 0
Weighted Average Fixed Pay Interest Rate	3.23%	0.00%
Weighted Average Variable Interest Rate	2.53%	0.00%