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, CAD in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) DerivativeInstrument	Dec. 31, 2016 USD ($) DerivativeInstrument	Mar. 31, 2017 GBP (£) DerivativeInstrument	Mar. 31, 2017 CAD DerivativeInstrument	Dec. 31, 2016 GBP (£) DerivativeInstrument	Dec. 31, 2016 CAD DerivativeInstrument
Interest Rate Caps [Member] | GBP [Member] | GBP LIBOR [Member]
Derivative [Line Items]
Number of Instruments	1	1	1	1	1	1
Notional Amount | £			£ 15,142		£ 15,142
Strike	2.00%	2.00%	2.00%	2.00%	2.00%	2.00%
Wtd. Avg. Maturity (Years)	1 month 6 days	3 months 18 days
Interest Rate Caps [Member] | USD [Member] | USD LIBOR [Member]
Derivative [Line Items]
Number of Instruments	19	21	19	19	21	21
Notional Amount | $	$ 633,903	$ 802,256
Strike	2.00%	2.00%	2.00%	2.00%	2.00%	2.00%
Wtd. Avg. Maturity (Years)	2 months 12 days	4 months 24 days
Interest Rate Caps [Member] | CAD [Member] | CDOR [Member]
Derivative [Line Items]
Number of Instruments	6	5	6	6	5	5
Notional Amount | CAD				CAD 304,931		CAD 400,035
Strike	2.00%	2.00%	2.00%	2.00%	2.00%	2.00%
Wtd. Avg. Maturity (Years)	2 months 12 days	4 months 24 days
Interest Rate Swaps [Member] | CAD [Member] | CDOR [Member]
Derivative [Line Items]
Number of Instruments	4	4	4	4	4	4
Notional Amount | CAD				CAD 108,271		CAD 108,271
Strike	1.00%	1.00%	1.00%	1.00%	1.00%	1.00%
Wtd. Avg. Maturity (Years)	2 years 2 months 12 days	2 years 4 months 24 days