Summary of Significant Accounting Policies (Schedule of Earnings Per Share Reconciliation) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income Attributable to Common Shareholders	$ 30,095	$ 56,306	$ 44,838	$ 96,327
Basic (in shares)	82,058	65,767	81,802	65,479
Effect of dilutive instruments	1,795	141	1,438	387
Diluted weighted average common shares outstanding	83,853	65,908	83,240	65,866
Net Income (Loss) - basic (in dollars per share)	$ 0.37	$ 0.86	$ 0.55	$ 1.47
Net Income (Loss) - diluted (in dollars per share)	$ 0.36	$ 0.85	$ 0.54	$ 1.46