Equity - Schedule of Dividend Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Dividends declared per share of common stock	$ 2.48	$ 2.48	$ 2.48
Percent taxable as ordinary dividends	100.00%	99.70%	97.20%
Percent taxable as capital gain dividends	0.00%	0.30%	2.80%
Percentage of taxable dividend	100.00%	100.00%	100.00%