Net Income per Common Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net Income per Common Share
Weighted average shares used for the basic net income per share computation	275,511,870	258,085,633	270,584,365	253,953,149
Incremental shares from share-based compensation	221,779	271,259	224,727	270,152
Weighted average shares used for diluted net income per share computation	276,050,671	258,673,914	271,126,114	254,540,323
Unvested Shares
Net Income per Common Share
Unvested shares from share-based compensation that were anti-dilutive	15,798	224	17,719	231
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	317,022
Unvested shares from share-based compensation that were anti-dilutive	88,182	97,312	88,182	235,446