Derivative Instruments and Hedging Activities - Interest Rate Swaps (Details) - Cash Flow Hedging - Designated as Hedging Instrument - Interest Rate Swap - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Notional Amount	$ 225,000	$ 360,000
Weighted Average Fixed Pay Interest Rate	0.90%	0.73%
Within 30 Days
Derivative [Line Items]
Notional Amount	$ 0	$ 0
Weighted Average Fixed Pay Interest Rate	0.00%	0.00%
Over 30 days to 3 months
Derivative [Line Items]
Notional Amount	$ 0	$ 0
Weighted Average Fixed Pay Interest Rate	0.00%	0.00%
Over 3 months to 6 months
Derivative [Line Items]
Notional Amount	$ 0	$ 0
Weighted Average Fixed Pay Interest Rate	0.00%	0.00%
Over 6 months to 12 months
Derivative [Line Items]
Notional Amount	$ 0	$ 135,000
Weighted Average Fixed Pay Interest Rate	0.00%	0.45%
Over 12 months to 24 months
Derivative [Line Items]
Notional Amount	$ 215,000	$ 0
Weighted Average Fixed Pay Interest Rate	0.83%	0.00%
Over 24 months to 36 months
Derivative [Line Items]
Notional Amount	$ 0	$ 215,000
Weighted Average Fixed Pay Interest Rate	0.00%	0.83%
Over 36 months to 48 months
Derivative [Line Items]
Notional Amount	$ 0	$ 0
Weighted Average Fixed Pay Interest Rate	0.00%	0.00%
Over 48 months to 60 months
Derivative [Line Items]
Notional Amount	$ 10,000	$ 10,000
Weighted Average Fixed Pay Interest Rate	2.25%	2.25%