Debt (Senior Convertible Notes) (Narrative) (Details) (USD $)	6 Months Ended									6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 4.0% Convertible Notes [Member]	Jun. 30, 2014 2011 4.0% Notes [Member]	Jun. 30, 2013 2011 4.0% Notes [Member]	Jun. 30, 2014 2009 4.0% Notes [Member]	Jun. 30, 2014 Unsecured Debt [Member] Convertible Debt [Member] 2011 4.25% Notes [Member]	Jun. 30, 2014 Unsecured Debt [Member] Convertible Debt [Member] 2011 4.25% Notes [Member] Plan [Member]	Dec. 31, 2013 Unsecured Debt [Member] Convertible Debt [Member] 2011 Convertible Notes [Member]	Jun. 30, 2014 Unsecured Debt [Member] Convertible Debt [Member] 4.25% Convertible Notes [Member]	Jun. 30, 2014 Unsecured Debt [Member] 4.0% Convertible Notes [Member]	Jun. 30, 2014 Unsecured Debt [Member] 2011 4.0% Notes [Member]	Jun. 30, 2014 Unsecured Debt [Member] 2009 4.0% Notes [Member]
Debt Instrument [Line Items]
Debt instrument, convertible, interest rate							4.25%			4.25%	4.00%	4.00%	4.00%
Debt instrument, convertible, maturity and conversion											$ 115,000,000	$ 105,300,000	$ 9,600,000
Debt instrument, convertible, maturity date							Dec. 15, 2014			Dec. 15, 2014	Jun. 15, 2014	Jun. 15, 2014	Jun. 15, 2014
Debt instrument, convertible, conversion ratio													0.0634417
Debt instrument, convertible, conversion rate denominator													1,000
Debt instrument, convertible, conversion price per share							$ 15.48			$ 15.48	$ 15.76	$ 15.76	$ 15.76
Debt instrument, convertible, common shares issued			4,200,000	3,600,000		600,000
Debt instrument, convertible, settlement in cash	105,325,000	150,000,000		105,300,000
Debt instrument, convertible, common shares issued, value				114,785,000	0
Debt instrument, convertible, share issuance from treasury stock			4,204,000
Debt instrument, convertible, unamortized debt discount and financing costs							$ 1,300,000		$ 4,000,000
Debt instrument, convertible, intent to refinance, description								The Company expects to settle the principal amount of its 2011 4.25% Notes on a long-term basis with proceeds from the Credit Facility, or through other sources of available funding, and the premium value in shares, and, therefore, has reflected the carrying amounts of these notes within long-term debt in the Company's condensed unaudited consolidated balance sheets.