Derivative Instruments and Hedging Activities - Other Derivative Instruments (Details) - Other Derivative Instruments - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Gross notional amount outstanding		$ 2,755,248	$ 2,665,358
Derivative asset fair value in other assets	[1]	21,019	17,079
Derivative liability fair value in other liabilities	[1]	(22,948)	(14,930)
Fair value of derivative	[2]	$ 22,682	$ 15,059

[1] Certain other derivative instruments are centrally cleared and their change in fair value is settled by the counterparties to the transaction, which results in no fair value.

[2] This amount represents the fair value if credit risk related contingent features were triggered.