Derivatives and Hedging Activities - Schedule of Interest Rate Derivatives (Details) - Designated as Hedging Instrument - Cash Flow Hedging - Swap $ in Thousands	Sep. 30, 2019 USD ($) derivative	Dec. 31, 2018 USD ($) derivative
Derivative [Line Items]
Number of Instruments | derivative	74	64
Notional Amount | $	$ 1,051,786	$ 596,567
GBP
Derivative [Line Items]
Number of Instruments | derivative	49	48
Notional Amount | $	$ 271,387	$ 234,312
EUR
Derivative [Line Items]
Number of Instruments | derivative	22	13
Notional Amount | $	$ 630,399	$ 212,255
USD
Derivative [Line Items]
Number of Instruments | derivative	3	3
Notional Amount | $	$ 150,000	$ 150,000