Stockholders' Equity - Cash Dividends (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Dividends Payable [Line Items]
Record Date			Jul. 30, 2015
Payment Date			Aug. 13, 2015
Per Share Amount	$ 0.09	$ 0.09	$ 0.18	$ 0.18
Total Dividend Paid			$ 9,509	$ 10,137
Cash Dividends Paid in February [Member]
Dividends Payable [Line Items]
Record Date			Feb. 05, 2015
Payment Date			Feb. 19, 2015
Per Share Amount			$ 0.09
Total Dividend Paid			$ 4,811
Cash Dividends Paid in May [Member]
Dividends Payable [Line Items]
Record Date			May 07, 2015
Payment Date			May 21, 2015
Per Share Amount			$ 0.09
Total Dividend Paid			$ 4,698