Other Debt - Convertible Senior Note Offering (Details) (USD $)		0 Months Ended		3 Months Ended		3 Months Ended	0 Months Ended	3 Months Ended			3 Months Ended
	Mar. 31, 2014	Jul. 29, 2013 Convertible Senior Notes [Member]	Mar. 31, 2014 Original 2018 Notes [Member] Convertible Senior Notes [Member]	Sep. 30, 2013 Original 2018 Notes [Member] Underwriter's Option to Purchase Addtional Notes, Proceeds [Member] Convertible Senior Notes [Member]	Mar. 31, 2014 Reopened 2018 Notes [Member] Convertible Senior Notes [Member]	Sep. 30, 2013 Reopened 2018 Notes [Member] Underwriter's Option to Purchase Addtional Notes, Proceeds [Member] Convertible Senior Notes [Member]	Dec. 10, 2013 2020 Notes [Member] Convertible Senior Notes [Member]	Mar. 31, 2014 2020 Notes [Member] Convertible Senior Notes [Member]	Mar. 31, 2014 Portion at Fair Value Measurement [Member] Original 2018 Notes [Member] Convertible Senior Notes [Member]	Mar. 31, 2014 Portion at Fair Value Measurement [Member] Reopened 2018 Notes [Member] Convertible Senior Notes [Member]	Mar. 31, 2014 Carrying (Reported) Amount, Fair Value Disclosure [Member] Original 2018 Notes [Member] Convertible Senior Notes [Member]	Mar. 31, 2014 Carrying (Reported) Amount, Fair Value Disclosure [Member] Reopened 2018 Notes [Member] Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Proceeds from issuance of convertible debt		$ 300,000,000		$ 10,000,000		$ 287,500,000	$ 402,500,000
Debt instrument, interest rate, stated percentage							3.75%
Long-term debt, fair value								389,700,000	299,600,000	282,100,000	301,000,000	282,500,000
Debt instrument, unamortized discount			10,400,000		5,400,000		12,800,000	26,300,000
Long-term debt	152,390,000							390,200,000
Debt instrument, convertible, conversion price, per conversion								66.0262			59.805
Shares converted per amount								$ 1,000			$ 1,000