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	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($) DerivativeInstrument	Dec. 31, 2017 USD ($) DerivativeInstrument	Mar. 31, 2018 CAD ($) DerivativeInstrument	Dec. 31, 2017 CAD ($) DerivativeInstrument
Interest Rate Caps [Member] | USD [Member] | USD LIBOR [Member]
Derivative [Line Items]
Number of Instruments	9	9	9	9
Notional Amount	$ 204,248	$ 204,248
Strike	2.40%	2.40%	2.40%	2.40%
Wtd. Avg. Maturity (Years)	1 year 2 months 12 days	1 year 6 months
Interest Rate Caps [Member] | CAD [Member] | CDOR [Member]
Derivative [Line Items]
Number of Instruments | DerivativeInstrument	3	3	3	3
Notional Amount			$ 22,765	$ 23,370
Strike	2.00%	2.00%	2.00%	2.00%
Wtd. Avg. Maturity (Years)	10 months 25 days	3 months 19 days
Interest Rate Swaps [Member] | CAD [Member] | CDOR [Member]
Derivative [Line Items]
Number of Instruments | DerivativeInstrument	4	4	4	4
Notional Amount			$ 108,004	$ 108,094
Strike	1.00%	1.00%	1.00%	1.00%
Wtd. Avg. Maturity (Years)	1 year 2 months 12 days	1 year 4 months 24 days