Income Taxes - Income Tax Characterization of Dividends (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Ordinary income	$ 1.24		$ 1.15
Capital gains	0.18	$ 0.83	0.01
Unrecaptured Section 1250 gains	0.26	0.66
Dividends paid per common share	$ 1.68	$ 1.49	$ 1.16
Percentage of Ordinary income	73.80%		99.40%
Percentage of Capital gains	10.70%	55.80%	0.60%
Percentage of Unrecaptured Section 1250 gains	15.50%	44.20%
Percentage of dividend paid per common share	100.00%	100.00%	100.00%