Stockholders' Equity - Schedule of Quarterly Cash Dividends to Common Stockholders (Detail) (USD $)	0 Months Ended		3 Months Ended		1 Months Ended
	Mar. 03, 2015	Jan. 05, 2015	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Mar. 31, 2015
Stockholders Equity [Line Items]
Dividend record date	Mar. 13, 2015	Jan. 13, 2015
Dividend payable date	Apr. 01, 2015	Jan. 22, 2015
Cash dividends declared	$ 0.21	$ 0.21	$ 0.42	$ 0.20
Q4 2014 Declaration [Member]
Stockholders Equity [Line Items]
Dividend record date			Jan. 13, 2015
Dividend payable date			Jan. 22, 2015
Cash dividends declared					$ 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						$ 0.21