Shareholders' Equity Shareholders' Equity (Details) (USD $) In Thousands, except Share data in Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Issuance of common shares	$ 23,783	$ 574,685
At-the-market equity issuance [Member]
Stock Issued During Period, Shares, New Issues	1.4
Issuance of common shares	23,800
At-the-market equity issuance [Member] | Gross Proceeds [Member]
Issuance of common shares	$ 24,100