Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended	9 Months Ended
	Oct. 31, 2016	Feb. 29, 2016	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Class of Warrant or Right [Line Items]
Stock repurchased during period (in shares)				13,500,000
Stock repurchased during period, number of unsettled shares			2,100,000	2,100,000
Stock repurchased during period, weighted average price per share				$ 8.02
Shares repurchased, value				$ 108.1
Common stock, beneficial ownership threshold to be considered an Acquiring Person (in hundredths)			5.00%	5.00%
Common shares purchasable per Right (in shares)			0.1	0.1
Shareholder rights accompanying each outstanding share of the company's common stock (in number of Rights)			1	1
Purchase price (in dollars per share)			$ 45	$ 45
Purchase price (in dollars per one-tenth share)			4.50	4.50
Redemption price (in dollars per Right)			$ 0.001	$ 0.001
Subsequent Event
Class of Warrant or Right [Line Items]
Stock repurchased during period (in shares)	4,800,000
Shares repurchased, value	$ 16.5
Rights
Class of Warrant or Right [Line Items]
Number of rights per outstanding share of common stock (in shares)				1
Period after public announcement that a person has become an acquirer (in days)				10 days
Period after a person announces a tender offer which would make them an acquirer (in days)				10 days
Convertible Senior Notes
Class of Warrant or Right [Line Items]
Extinguishment of debt amount				$ 188.5
Stated interest rate (in hundredths)			5.00%	5.00%	5.00%	5.00%
9% Debentures
Class of Warrant or Right [Line Items]
Extinguishment of debt amount		$ 132.7
Stated interest rate (in hundredths)			9.00%	9.00%		9.00%
Reacquisition of convertible junior subordinated debentures-equity component				$ (6.3)
2% Convertible Senior Notes | Convertible Senior Notes
Class of Warrant or Right [Line Items]
Extinguishment of debt amount			$ 292.4
Stated interest rate (in hundredths)			2.00%	2.00%
Shares issued for repayment of debt			18,300,000