Stockholders' Equity - Schedule of Quarterly Cash Dividends to Common Stockholders (Detail) - $ / shares				1 Months Ended			3 Months Ended		6 Months Ended
	Jun. 10, 2015	Mar. 03, 2015	Jan. 05, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Stockholders Equity [Line Items]
Dividend record date	Jun. 22, 2015	Mar. 13, 2015	Jan. 13, 2015
Dividend payable date	Jul. 01, 2015	Apr. 01, 2015	Jan. 22, 2015
Cash dividends declared per share	$ 0.21	$ 0.21	$ 0.21				$ 0.21	$ 0.21	$ 0.63	$ 0.41
Q4 2014 Declaration [Member]
Stockholders Equity [Line Items]
Dividend record date									Jan. 13, 2015
Dividend payable date									Jan. 22, 2015
Cash dividends declared per share						$ 0.21
Q1 2015 Declaration [Member]
Stockholders Equity [Line Items]
Dividend record date									Mar. 13, 2015
Dividend payable date									Apr. 01, 2015
Cash dividends declared per share					$ 0.21
Q2 2015 Declaration [Member]
Stockholders Equity [Line Items]
Dividend record date									Jun. 22, 2015
Dividend payable date									Jul. 01, 2015
Cash dividends declared per share				$ 0.21