Organization and Significant Accounting Policies (Details 9) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013 2 3/4 percent convertible senior notes	Dec. 31, 2012 2 3/4 percent convertible senior notes	Aug. 31, 2012 2 3/4 percent convertible senior notes	Sep. 30, 2012 2 5/8 percent convertible subordinated notes
Long-term obligations
Interest rate on convertible debt (as a percent)	2.75%			2.625%
Debt issued	$ 201,250	$ 201,250	$ 201,300