Cash Dividends (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Dividends Payable [Line Items]
Cash dividends paid, per share	$ 0.02	$ 0.02	$ 0.04	$ 0.12
Cash dividends paid			$ 7,595	$ 17,665
Installment 1, FY 2017
Dividends Payable [Line Items]
Cash dividends paid, date			Mar. 22, 2017
Cash dividends paid, per share			$ 0.02
Cash dividends paid			$ 3,326
Installment 2, FY 2017
Dividends Payable [Line Items]
Cash dividends paid, date			Jun. 22, 2017
Cash dividends paid, per share			$ 0.02
Cash dividends paid			$ 4,269
Installment 1, FY 2016
Dividends Payable [Line Items]
Cash dividends paid, date				Mar. 24, 2016
Cash dividends paid, per share				$ 0.10
Cash dividends paid				$ 14,712
Installment 2, FY 2016
Dividends Payable [Line Items]
Cash dividends paid, date				Jun. 23, 2016
Cash dividends paid, per share				$ 0.02
Cash dividends paid				$ 2,953