Debt (Senior Convertible Notes) (Narrative) (Details) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended		12 Months Ended
	Dec. 31, 2014 USD ($) $ / shares shares	Jun. 30, 2014 USD ($) shares	Dec. 31, 2014 $ / shares shares
4.25% Convertible Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares	$ 15.48		$ 15.48
4.25% Convertible Notes [Member] | Common Stock [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, common shares issued (in shares)	2.4
2009 4.25% Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, conversion ratio (in shares per dollar)			0.0646162
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares	$ 15.48		$ 15.48
2009 4.25% Notes [Member] | Common Stock [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, common shares issued (in shares)	0.2
2011 4.25% Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, conversion ratio (in shares per dollar)			0.0646162
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares	$ 15.48		$ 15.48
2011 4.25% Notes [Member] | Common Stock [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, common shares issued (in shares)	2.2
4.0% Convertible Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares	$ 15.76		$ 15.76
4.0% Convertible Notes [Member] | Common Stock [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, common shares issued (in shares)		4.2
2009 4.0% Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, conversion ratio (in shares per dollar)			0.0634417
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares	15.76		$ 15.76
2009 4.0% Notes [Member] | Common Stock [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, common shares issued (in shares)		0.6
2011 4.0% Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, conversion ratio (in shares per dollar)			0.0634417
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares	$ 15.76		$ 15.76
2011 4.0% Notes [Member] | Common Stock [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, common shares issued (in shares)		3.6
Convertible Debt [Member]
Debt Instrument [Line Items]
Share reissuances, treasury stock (in shares)			6.6
Convertible Debt [Member] | 4.25% Convertible Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, interest rate (percentage)	4.25%		4.25%
Debt instrument, convertible, maturity date			Dec. 15, 2014
Share reissuances, treasury stock (in shares)	2.4
Convertible Debt [Member] | 2009 4.25% Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, interest rate (percentage)	4.25%		4.25%
Convertible Debt [Member] | 2011 4.25% Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, interest rate (percentage)	4.25%		4.25%
Convertible Debt [Member] | 2011 4.25% Notes [Member] | Common Stock [Member]
Debt Instrument [Line Items]
Value of premium shares upon conversion, convertible notes (in dollars) | $	$ 41.0
Convertible Debt [Member] | 4.0% Convertible Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, interest rate (percentage)	4.00%		4.00%
Debt instrument, convertible, maturity date			Jun. 15, 2014
Share reissuances, treasury stock (in shares)		4.2
Convertible Debt [Member] | 2009 4.0% Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, interest rate (percentage)	4.00%		4.00%
Convertible Debt [Member] | 2011 4.0% Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, interest rate (percentage)	4.00%		4.00%
Convertible Debt [Member] | 2011 4.0% Notes [Member] | Common Stock [Member]
Debt Instrument [Line Items]
Value of premium shares upon conversion, convertible notes (in dollars) | $		$ 114.8