Net Income Per Common Share (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net Income Per Common Share
Weighted average shares used for the basic net income per share computation	220,979,955	195,574,014	214,039,692	183,714,191
Incremental shares from share-based compensation	63,664	185,077	49,937	159,456
Weighted average shares used for diluted net income per share computation	221,360,641	196,076,113	214,406,651	184,153,887
Unvested Shares
Net Income Per Common Share
Unvested shares from share-based compensation that were anti-dilutive	59,149	16,600	59,569	16,600
Convertible Partnership Units
Net Income Per Common Share
Weighted average partnership common units convertible to common shares that were dilutive	317,022	317,022	317,022	280,240
Unvested shares from share-based compensation that were anti-dilutive	529,161	23,497	531,839	11,813