Net Income per Common Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net Income per Common Share
Weighted average shares used for the basic net income per share computation	290,664,368	275,511,870	286,599,191	270,584,365
Incremental shares from share-based compensation	225,796	221,779	189,072	224,727
Weighted average shares used for diluted net income per share computation	291,207,186	276,050,671	287,105,285	271,126,114
Unvested Shares
Net Income per Common Share
Unvested shares from share-based compensation that were anti-dilutive	261	15,798	1,378	17,719
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	397,690	88,182	271,890	88,182