Derivative Instruments and Hedging Activities (Details) - Cash Flow Hedges - Cash Flow Hedging - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross notional amount outstanding	$ 1,420,000,000	$ 1,220,000,000
Derivative asset fair value	20,683,000	4,787,000
Derivative liability fair value	$ (19,647,000)	$ (8,950,000)
Weighted-average interest rate received	1.28%	1.24%
Weighted-average interest rate paid	1.01%	0.75%
Weighted-average maturity (in years)	3 years 3 months 15 days	3 years 10 months 28 days