Equity - Summary of Dividend Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
First Quarter Dividend
Dividends Payable [Line Items]
Declaration Date	Feb. 17, 2017	Feb. 17, 2016
Record Date	Mar. 01, 2017	Feb. 29, 2016
Payment Date	Mar. 20, 2017	Mar. 17, 2016
Dividend per share (in usd per share)	$ 0.10	$ 0.10
Second Quarter Dividend
Dividends Payable [Line Items]
Declaration Date	Apr. 27, 2017	May 11, 2016
Record Date	May 08, 2017	May 23, 2016
Payment Date	Jun. 09, 2017	Jun. 10, 2016
Dividend per share (in usd per share)	$ 0.10	$ 0.10
Third Quarter Dividend
Dividends Payable [Line Items]
Declaration Date	Jul. 25, 2017	Jul. 28, 2016
Record Date	Aug. 07, 2017	Aug. 09, 2016
Payment Date	Sep. 08, 2017	Sep. 02, 2016
Dividend per share (in usd per share)	$ 0.10	$ 0.10
Fourth Quarter Dividend
Dividends Payable [Line Items]
Declaration Date		Oct. 27, 2016
Record Date		Nov. 14, 2016
Payment Date		Dec. 02, 2016
Dividend per share (in usd per share)		$ 0.10