Derivative Instruments and Hedging Activities - Offsetting Derivatives (Details) - USD ($) $ in Thousands		Jun. 30, 2019	Dec. 31, 2018
Assets
Gross amounts recognized		$ 59,905	$ 32,057
Less: amounts offset in the Consolidated Statements of Financial Condition		0	0
Net amount presented in the Consolidated Statements of Financial Condition	[1]	59,905	32,057
Offsetting derivative positions		(4,088)	(11,678)
Cash collateral pledged		0	(9,060)
Net credit exposure		55,817	11,319
Liabilities
Gross amounts recognized		23,191	28,861
Less: amounts offset in the Consolidated Statements of Financial Condition		0	0
Net amount presented in the Consolidated Statements of Financial Condition	[1]	23,191	28,861
Offsetting derivative positions		(4,088)	(11,678)
Cash collateral pledged		(12,618)	(3,506)
Net credit exposure		$ 6,485	$ 13,677

[1] Included in other assets or other liabilities in the Consolidated Statements of Financial Condition.