Summary of Dividends Declared (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Dividends Payable [Line Items]
Payment of dividends to stockholders	$ 71,947	$ 45,991
February 8, 2016
Dividends Payable [Line Items]
Declaration Date	Feb. 08, 2016
Dividend Per Share	$ 0.24
Record Date	Mar. 10, 2016
Payment of dividends to stockholders	$ 36,174
Payment Date	Mar. 30, 2016
April 26, 2016
Dividends Payable [Line Items]
Declaration Date	Apr. 26, 2016
Dividend Per Share	$ 0.24
Record Date	May 26, 2016
Payment of dividends to stockholders	$ 35,773
Payment Date	Jun. 16, 2016
February 4, 2015
Dividends Payable [Line Items]
Declaration Date		Feb. 04, 2015
Dividend Per Share		$ 0.18
Record Date		Mar. 10, 2015
Payment of dividends to stockholders		$ 22,895
Payment Date		Mar. 26, 2015
April 29, 2015
Dividends Payable [Line Items]
Declaration Date		Apr. 29, 2015
Dividend Per Share		$ 0.18
Record Date		May 28, 2015
Payment of dividends to stockholders		$ 23,096
Payment Date		Jun. 18, 2015