Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Class of Warrant or Right [Line Items]
Common stock, beneficial ownership threshold to be considered an Acquiring Person (in hundredths)	5.00%
Common shares purchasable per Right (in shares)	0.1
Shareholder rights accompanying each outstanding share of the company's common stock (in number of Rights)	1
Purchase price (in dollars per share)	$ 45
Purchase price (in dollars per one-tenth share)	4.50
Redemption price (in dollars per Right)	$ 0.001
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 Junior Subordinated Debentures, interest at 9% per annum, due April 2063
Class of Warrant or Right [Line Items]
Stated interest rate (in hundredths)	9.00%	9.00%
Reacquisition of convertible junior subordinated debentures-equity component	$ (9.8)