Equity - Summary of Class A Common Stock Issuances (Detail) - USD ($)	1 Months Ended	12 Months Ended
	May 31, 2013	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Shares issued	25,875,000	10,535,842	14,568,431	12,421,401
Net proceeds		$ 372,337,000	$ 476,420,000	$ 391,558,000
Class A Common Stock [Member]
Class of Stock [Line Items]
Shares issued		10,534,628	14,566,743	12,420,000
Gross share issue price		$ (35.75)	$ 33.16	$ 31.90
Net share issue price		$ (35.38)	$ 32.76	$ 31.57
Net proceeds		$ (372,341)	$ 476,420	$ 391,558