Summary of Significant Accounting Policies (Detail 2)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Weighted Average Number of Shares Outstanding, Basic	218,390,885	191,754,857	132,817,472
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	59,978	26,765	67,461
Weighted average shares used for diluted net income per share computation	218,767,885	191,781,622	132,884,933
Convertible Partnership Units
Weighted average shares used for diluted net income per share computation	317,022
Weighted average partnership common units convertible to common shares that were anti-dilutive	523,847	851,568
Unvested Shares
Weighted average partnership common units convertible to common shares that were anti-dilutive	51,749	59,629	17,570