Organization and Significant Accounting Policies - Summary of Earnings (Loss) Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Basic weighted-average shares (in shares)	23,872	23,365	23,101
Conversion of unsecured loan notes (in shares)	0	0	0
Unexercised options and unvested restricted stock units (in shares)	0	0	0
Diluted weighted-average shares (in shares)	23,872	23,365	23,101