Earnings (loss) percommon share (Details 11) - shares shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Weighted average common shares outstanding - basic	195,304	195,304	195,304	195,284	195,266	195,151	194,805	194,479	195,299	194,928	192,507
Effect of dilutive performance share awards									319	58	80
Weighted average common shares outstanding - diluted	195,889	195,811	195,699	195,284	195,324	195,169	194,838	194,566	195,618	194,986	192,587
Shares excluded from the calculation of diluted earnings per share									0	0	0