Equity - Summary of Class A Common Stock Issuances (Parenthetical) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Shares Issued	100,000	28,275,006	25,875,000	669,047
Weighted average issue price	$ 27.58
Net Proceeds	$ 2,800	$ 766,138	$ 633,807	$ 10,000