Shareholders' Equity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Proceeds from issuance of common shares, net	$ 34,913	$ 13,383	$ 220,258
At-the-market equity issuance [Member]
Proceeds from issuance of common shares, net	$ 28,400		$ 215,600
Stock Issued During Period, Shares, New Issues	990,400		8,400,000
At-the-market equity issuance [Member] | Gross Proceeds [Member]
Proceeds from issuance of common shares, net			$ 218,200
At-the-market equity issuance [Member] | Gross Proceeds [Member]
Proceeds from issuance of common shares, net	$ 29,000