Earnings per Share - Dilutive and Antidilutive securities (Details) shares in Thousands, instrument in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) instrument shares	Mar. 31, 2015 shares
2017 Notes
Antidilutive securities and effect of dilutive securities
Amount by which if-converted value of the Notes are less than principal amount | $	$ 90.5
2018 Notes
Antidilutive securities and effect of dilutive securities
Amount by which if-converted value of the Notes are less than principal amount | $	72.2
2019 Notes
Antidilutive securities and effect of dilutive securities
Amount by which if-converted value of the Notes are less than principal amount | $	$ 23.4
Convertible Senior Notes
Antidilutive securities and effect of dilutive securities
Potential shares of common stock contingently issuable upon conversion of the Convertible Notes | instrument	62.7
Shares excluded from diluted EPS calculations | shares	62,700
Effect of dilutive securities - Convertible Notes (in shares) | shares	0	5,353
Restricted stock
Antidilutive securities and effect of dilutive securities
Number of anti-dilutive common shares excluded from the calculation of diluted income per share | shares	1,500	1,800