Derivative Financial Instruments - Summary of Derivative Positions (Details) - 3 months ended Mar. 31, 2019	USD ($) € / £ $ / £	GBP (£) € / £ $ / £
USD/British Pound | Sell
Derivative [Line Items]
Notional Amount		£ 3,552,000
Weighted Average Remaining Maturity In Years	3 months 19 days
Average Exchange Rate | $ / £	1.31	1.31
EURO/British Pound | Sell
Derivative [Line Items]
Notional Amount		£ 2,568,300
Weighted Average Remaining Maturity In Years	3 months 19 days
Average Exchange Rate | € / £	1.16	1.16
Interest Rate Swaps
Derivative [Line Items]
Notional Amount | $	$ 206,718,750
Weighted Average Remaining Maturity In Years	3 years 9 months