v2.4.0.8

Measured on Recurring Basis (Details) (USD $) |  |  |  |  |  | 6 Months Ended |  |  |  |  |  |
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Sep. 30, 2014 | Mar. 31, 2014 | Sep. 30, 2013 | Mar. 31, 2013 | Sep. 30, 2014 Insurance Sector Auction Rate Securities [Member] | Sep. 30, 2014 Insurance Sector Auction Rate Securities [Member] Minimum [Member] | Sep. 30, 2014 Insurance Sector Auction Rate Securities [Member] Maximum [Member] | Sep. 30, 2014 Fair Value, Inputs, Level 1 [Member] | Mar. 31, 2014 Fair Value, Inputs, Level 1 [Member] | Sep. 30, 2014 Fair Value, Inputs, Level 2 [Member] | Mar. 31, 2014 Fair Value, Inputs, Level 2 [Member] | Sep. 30, 2014 Fair Value, Inputs, Level 3 [Member] | Mar. 31, 2014 Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Money Market Fund Deposits Fair Value Disclosure | $ 95,464,000 | $ 192,159,000 |  |  |  |  |  | $ 95,464,000 | $ 192,159,000 | $ 0 | $ 0 | $ 0 | $ 0
Corporate Bonds and Debt Fair Value Disclosure | 905,593,000 | 943,966,000 |  |  |  |  |  | 0 | 0 | 899,403,000 | 937,776,000 | 6,190,000 | 6,190,000
Time Deposits Fair Value Disclosure | 20,160,000 |  |  |  |  |  |  | 0 |  | 20,160,000 |  | 0 |
Government Agency Bonds Fair Value Disclosure | 666,208,000 | 681,394,000 |  |  |  |  |  | 0 | 0 | 666,208,000 | 681,394,000 | 0 | 0
Cash Deposit Accounts Fair Value Disclosure | 385,975,000 | 274,444,000 |  |  |  |  |  | 0 | 0 | 385,975,000 | 274,444,000 | 0 | 0
Municipal Bonds Fair Value Disclosure | 41,161,000 | 41,709,000 |  |  |  |  |  | 0 | 0 | 41,161,000 | 41,709,000 | 0 | 0
Auction Rate Securities Fair Value Disclosure | 9,825,000 | 9,825,000 |  |  |  |  |  | 0 | 0 | 0 | 0 | 9,825,000 | 9,825,000
Fair Value, Assets and Liabilities, as Classified on the Condensed Consolidated Balance Sheets [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Cash and cash equivalents | 481,439,000 | 466,603,000 | 344,202,000 | 528,334,000 |  |  |  | 95,464,000 | 192,159,000 | 385,975,000 | 274,444,000 | 0 | 0
Short-term investments | 801,670,000 | 878,182,000 |  |  |  |  |  | 0 | 0 | 801,670,000 | 878,182,000 | 0 | 0
Long-term investments | 841,277,000 | 798,712,000 |  |  |  |  |  | 0 | 0 | 825,262,000 | 782,697,000 | 16,015,000 | 16,015,000
Total assets measured at fair value | 2,124,386,000 | 2,143,497,000 |  |  |  |  |  | 95,464,000 | 192,159,000 | 2,012,907,000 | 1,935,323,000 | 16,015,000 | 16,015,000
Available-for-sale Securities, Other Disclosure Items [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |
Value of auction rate securities for which recent auctions were unsuccessful |  |  |  |  | 9,800,000 |  |  |  |  |  |  |  |
Discount rate |  |  |  |  |  | 2.00% | 2.50% |  |  |  |  |  |
Auction Rate Securities Par Value |  |  |  |  | $ 22,400,000 |  |  |  |  |  |  |  |
Liquidity risk premium (percentage) |  |  |  |  |  | 9.10% | 29.50% |  |  |  |  |  |
Anticipated liquidity horizon |  |  |  |  |  | 7 years | 10 years |  |  |  |  |  |

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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 + Details
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- Definition Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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