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Earnings Per Share - Antidilutive Securities Excluded from Computation of EPS (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2010
Convertible Notes due 2017 [Member] \| Senior notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt Instrument, convertible, conversion price (in dollars per share)				$ 11.00
Convertible Notes due 2021 [Member] \| Senior notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt Instrument, convertible, conversion price (in dollars per share)	$ 9.33
Stock options and restricted stock awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average antidilutive securities excluded from computation of EPS (in shares)	1,495	7,419	7,482
Convertible notes [Member] \| Convertible Notes due 2017 [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average antidilutive securities excluded from computation of EPS (in shares)	0	5,702	14,295