Net Income Per Common Share (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net Income Per Common Share
Weighted average shares used for the basic net income per share computation	222,061,661	195,768,298	216,804,815	187,805,222
Incremental shares from share-based compensation	174,410		25,198	114,018
Weighted average shares used for diluted net income per share computation	222,236,071	196,619,866	217,147,035	188,399,848
Unvested Shares
Net Income Per Common Share
Unvested shares from share-based compensation that were anti-dilutive	45,654	60,259	58,564	59,749
Convertible Partnership Units
Net Income Per Common Share
Weighted average partnership common units convertible to common shares that were dilutive		851,568	317,022	480,608
Weighted average partnership common units convertible to common shares that were anti-dilutive	841,568		529,381