Shareholders' Equity Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended					6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Apr. 30, 2014 Prior to Increase Approved by Shareholders [Member]	Apr. 30, 2014 After Increase Approved by Shareholders [Member]	Jun. 30, 2014 At-the-market equity issuance [Member]	Jun. 30, 2014 At-the-market equity issuance [Member] Gross Proceeds [Member]
Stock Issued During Period, Shares, New Issues						11,000,000
Issuance of common shares	$ 191,107	$ 601,927				$ 191,100	$ 193,100
Common Stock, Shares Authorized	600,000,000		400,000,000	400,000,000	600,000,000