Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 3,221	$ 23,312
Weighted average common shares outstanding - basic (in shares)	112,017	111,728
Net effect of dilutive securities:
Contingently issuable performance shares and restricted stock units (in shares)	476	467
Weighted average common shares outstanding — diluted (in shares)	112,493	112,195
Earnings per weighted-average common share outstanding
Net income attributable to common shareholders - basic (in dollars per share)	$ 0.03	$ 0.21
Net income attributable to common shareholders - diluted (in dollars per share)	$ 0.03	$ 0.21