Derivative Instruments and Hedging Activities - Cash Flow Hedge Accounting on AOCI (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest Income
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains (losses) recognized in other comprehensive income	$ 18,776	$ 11,150	$ (4,674)
Reclassification of gains (losses) included in net income	2,611	5,159	7,641
Interest Expense
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains (losses) recognized in other comprehensive income	(20,500)	(8,025)	(1,068)
Reclassification of gains (losses) included in net income	$ (3,673)	$ (3,951)	$ (4,074)