Derivative Financial Instruments - Summary of Outstanding Interest Rate Derivatives Designated as Cash Flow Hedges of Interest Rate Risk (Detail) - Cash Flow Hedges [Member] - Designated as Hedging Instrument [Member] $ in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019 CAD ($) DerivativeInstrument	Dec. 31, 2018 CAD ($) DerivativeInstrument	Sep. 30, 2019 USD ($) DerivativeInstrument	Dec. 31, 2018 USD ($) DerivativeInstrument
Interest Rate Caps [Member] | USD [Member] | USD LIBOR [Member]
Derivative [Line Items]
Number of Instruments | DerivativeInstrument	1	9	1	9
Notional Amount | $			$ 7,296	$ 204,248
Strike	2.30%	2.40%	2.30%	2.40%
Wtd. Avg. Maturity (Years)	2 months 12 days	6 months
Interest Rate Caps [Member] | CAD [Member] | CDOR [Member]
Derivative [Line Items]
Number of Instruments | DerivativeInstrument	1	2	1	2
Notional Amount | $	$ 21,709	$ 39,998
Strike	3.00%	2.50%	3.00%	2.50%
Wtd. Avg. Maturity (Years)	2 months 12 days	7 months 6 days
Interest Rate Swaps [Member] | CAD [Member] | CDOR [Member]
Derivative [Line Items]
Number of Instruments | DerivativeInstrument	2	3	2	3
Notional Amount | $	$ 17,273	$ 90,472
Strike	1.00%	1.00%	1.00%	1.00%
Wtd. Avg. Maturity (Years)	10 months 24 days	6 months