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Fair Value of Financial Instruments (Details 2) (USD $)
In Thousands, unless otherwise specified |
9 Months Ended | 3 Months Ended | 9 Months Ended | ||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Sep. 30, 2013
Minimum
|
Sep. 30, 2013
Maximum
|
Sep. 30, 2013
3.375% Senior Notes
|
Dec. 31, 2012
3.375% Senior Notes
|
Sep. 30, 2011
3.375% Senior Notes
|
Sep. 30, 2013
1.5% Convertible Senior Notes
|
Dec. 31, 2012
1.5% Convertible Senior Notes
|
Feb. 29, 2004
1.5% Convertible Senior Notes
|
Mar. 31, 2013
5.625% Municipal Bonds
|
Sep. 30, 2013
5.625% Municipal Bonds
|
Dec. 31, 2012
5.625% Municipal Bonds
|
Sep. 30, 2013
Carrying Value
|
Dec. 31, 2012
Carrying Value
|
Sep. 30, 2013
Carrying Value
Other borrowings
|
Sep. 30, 2013
Carrying Value
3.375% Senior Notes
|
Dec. 31, 2012
Carrying Value
3.375% Senior Notes
|
Sep. 30, 2013
Carrying Value
1.5% Convertible Senior Notes
|
Dec. 31, 2012
Carrying Value
1.5% Convertible Senior Notes
|
Dec. 31, 2012
Carrying Value
5.625% Municipal Bonds
|
Dec. 31, 2012
Carrying Value
Notes payable, including noncurrent portion
|
Sep. 30, 2013
Fair Value
Level 1
|
Dec. 31, 2012
Fair Value
Level 1
|
Sep. 30, 2013
Fair Value
Level 2
|
Dec. 31, 2012
Fair Value
Level 2
|
Sep. 30, 2013
Fair Value
Level 3
|
Dec. 31, 2012
Fair Value
Level 3
|
Sep. 30, 2013
Fair Value
Other borrowings
Level 2
|
Sep. 30, 2013
Fair Value
3.375% Senior Notes
Level 2
|
Dec. 31, 2012
Fair Value
3.375% Senior Notes
Level 2
|
Sep. 30, 2013
Fair Value
1.5% Convertible Senior Notes
Level 2
|
Dec. 31, 2012
Fair Value
1.5% Convertible Senior Notes
Level 2
|
Dec. 31, 2012
Fair Value
5.625% Municipal Bonds
Level 2
|
Dec. 31, 2012
Fair Value
Notes payable, including noncurrent portion
Level 3
|
|
| Estimated fair values of the company's financial instruments that are not measured at fair value on a recurring basis | |||||||||||||||||||||||||||||||||
| Cash | $ 1,604,552 | $ 1,343,866 | $ 1,604,552 | $ 1,343,866 | |||||||||||||||||||||||||||||
| Cash equivalents | 913,904 | 796,218 | 913,904 | 796,218 | |||||||||||||||||||||||||||||
| Marketable securities, current | 22,812 | 34,688 | 22,812 | 34,688 | |||||||||||||||||||||||||||||
| Notes receivable, including noncurrent portion | 25,836 | 34,471 | 25,836 | 34,471 | |||||||||||||||||||||||||||||
| Debt | $ 7,035 | $ 496,494 | $ 496,164 | $ 18,398 | $ 18,472 | $ 17,795 | $ 8,566 | $ 7,035 | $ 493,992 | $ 527,219 | $ 47,510 | $ 39,392 | $ 17,878 | $ 8,566 | |||||||||||||||||||
| Debt instrument interest rate (as a percent) | 3.375% | 3.375% | 3.375% | 1.50% | 1.50% | 1.50% | 5.625% | ||||||||||||||||||||||||||
| Redemption price as a percentage of the principal amount of bonds (as a percent) | 100.00% | 100.00% | |||||||||||||||||||||||||||||||
| Notes payable, maturity period | 1 year | 4 years | |||||||||||||||||||||||||||||||