Earnings (loss) percommon share (Details 12) - shares shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Weighted average common shares outstanding - basic	195,266	195,151	194,805	194,479	194,136	193,949	192,060	189,820	194,928	192,507	188,855
Effect of dilutive performance share awards									58	80	838
Weighted average common shares outstanding - diluted	195,324	195,169	194,838	194,566	194,219	194,300	192,659	190,432	194,986	192,587	189,693
Shares excluded from the calculation of diluted earnings per share									0	0	0