Derivatives and Hedging Activities - Foreign Cross Currency Derivatives (Details) - Not Designated as Hedging Instrument - Swap $ in Thousands	Jun. 30, 2019 USD ($) derivative	Dec. 31, 2018 USD ($) derivative
Derivative [Line Items]
Number of Instruments (derivative) | derivative	71	93
Notional Amount | $	$ 72,302	$ 221,125
Foreign currency forwards | GBP
Derivative [Line Items]
Number of Instruments (derivative) | derivative	40	50
Notional Amount | $	$ 32,500	$ 43,000
Foreign currency forwards | EUR
Derivative [Line Items]
Number of Instruments (derivative) | derivative	30	38
Notional Amount | $	$ 29,000	$ 39,500
Interest rate swaps, net | EUR
Derivative [Line Items]
Number of Instruments (derivative) | derivative	1	5
Notional Amount | $	$ 10,802	$ 138,625