Derivative Instruments and Hedging Activities (Details) - Cash Flow Hedges - Cash Flow Hedging - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gross notional amount outstanding	$ 1,470,000	$ 1,220,000
Derivative asset fair value	5,402	4,787
Derivative liability fair value	$ (7,390)	$ (8,950)
Weighted-average interest rate received	1.37%	1.24%
Weighted-average interest rate paid	1.11%	0.75%
Weighted-average maturity (in years)	2 years 9 months 28 days	3 years 10 months 28 days