Debt (Senior Convertible Notes) (Narrative) (Details) (USD $)	9 Months Ended		1 Months Ended	9 Months Ended		1 Months Ended			9 Months Ended	1 Months Ended					9 Months Ended						1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2014 4.0% Convertible Notes [Member] Common Stock [Member]	Sep. 30, 2014 2011 4.0% Notes [Member]	Sep. 30, 2013 2011 4.0% Notes [Member]	Jun. 30, 2014 2011 4.0% Notes [Member] Common Stock [Member]	Jun. 30, 2014 2009 4.0% Notes [Member] Common Stock [Member]	Jun. 30, 2014 Convertible Debt [Member] 4.0% Convertible Notes [Member]	Sep. 30, 2014 Convertible Debt [Member] 4.0% Convertible Notes [Member]	Jun. 30, 2014 Convertible Debt [Member] 2011 4.0% Notes [Member]	Jun. 30, 2014 Convertible Debt [Member] 2011 4.0% Notes [Member] Common Stock [Member]	Sep. 30, 2014 Unsecured Debt [Member] 4.25% Convertible Notes [Member]	Sep. 30, 2014 Unsecured Debt [Member] 2011 4.25% Notes [Member]	Sep. 30, 2014 Unsecured Debt [Member] 4.0% Convertible Notes [Member]	Sep. 30, 2014 Unsecured Debt [Member] 2011 4.0% Notes [Member]	Sep. 30, 2014 Unsecured Debt [Member] 2009 4.0% Notes [Member]	Sep. 30, 2014 Unsecured Debt [Member] Convertible Debt [Member] 4.25% Convertible Notes [Member]	Sep. 30, 2014 Unsecured Debt [Member] Convertible Debt [Member] 2011 4.25% Notes [Member]	Sep. 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] 4.0% Convertible Notes [Member]	Sep. 30, 2014 Unsecured Debt [Member] Convertible Debt [Member] 4.0% Convertible Notes [Member]	Jun. 30, 2014 Unsecured Debt [Member] Convertible Debt [Member] 2011 4.0% Notes [Member]	Sep. 30, 2014 Unsecured Debt [Member] Convertible Debt [Member] 2011 4.0% Notes [Member]	Jun. 30, 2014 Unsecured Debt [Member] Convertible Debt [Member] 2009 4.0% Notes [Member]	Sep. 30, 2014 Unsecured Debt [Member] Convertible 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, matured and converted																					$ 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	0.0634417
Debt instrument, convertible, conversion rate denominator																								1,000		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, settlement in cash	105,325,000	150,000,000								105,300,000
Debt instrument, convertible, common shares issued, value				114,785,000	0						114,800,000
Debt instrument, convertible, shares reissued from treasury								4,200,000	4,204,000
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, consistent with the settlement of the 2011 4.0% Notes in June 2014. Therefore, the Company has reflected the carrying amounts of these notes within long-term debt in the condensed unaudited consolidated balance sheets.
Debt instrument, convertible, unamortized debt discount and financing costs																		$ 600,000		$ 4,000,000