Debt (Details) (USD $)	3 Months Ended		6 Months Ended		0 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 16, 2014 Convertible Debt [Member]	Jun. 12, 2014 Convertible Debt [Member]	Jun. 15, 2014 Convertible Debt [Member]	Jun. 12, 2014 Convertible Debt [Member]	Jun. 30, 2013 Convertible Debt [Member]
Debt Instrument [Line Items]
Principal amount of debt converted						$ 271,800,000
Stated interest rate on convertible senior notes (as a percent)							5.125%	5.125%	5.125%
Convertible debt rate, basis for conversion						0.0584731
Conversion price per share (in dollars per share)								$ 17.10
Shares issued upon conversion						15,893,457
Remaining outstanding Notes paid in cash	$ 76,412,000	$ 202,312,000	$ 132,658,000	$ 508,003,000	$ 15,700,000