Shareholders' Equity (Tables)

3 Months Ended

Mar. 31, 2014

Equity [Abstract]

Schedule of Common Stock Outstanding Roll Forward [Table Text Block]

The following table presents a summary of the changes in the number of common shares outstanding for the periods presented:

	Three Months Ended
	March 31,
	2014		2013
Balance as of beginning of period	54,310,484		54,268,915
Common stock issued under DRIP	3,938		298,304
Common stock issued under ATM program	—		180,986
Common stock issued or redeemed under stock and incentive plans	442,035		139,600
Common stock forfeited for tax withholding on share-based compensation	(59,150	)	(52,385	)
Balance as of end of period	54,697,307		54,835,420

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

The following table presents a rollforward of the restricted stock activity for the periods indicated:

	Three Months Ended
	March 31,
	2014		2013
Restricted stock outstanding as of beginning of period	520,969		448,283
Restricted stock granted	428,363		139,600
Restricted stock vested	(188,620	)	(153,720	)
Restricted stock outstanding as of end of period	760,712		434,163