Investments (Tables)
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6 Months Ended |
Sep. 30, 2017 |
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| Investments [Abstract] |
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| Summary of available-for-sale securities |
The following is a summary of available-for-sale securities at September 30, 2017 (amounts in thousands): | | | | | | | | | | | | | | | | | | Available-for-sale Securities | | Adjusted Cost | | Gross Unrealized Gains | | Gross Unrealized Losses | | Estimated Fair Value | Government agency bonds | $ | 612,396 |
| | $ | 12 |
| | $ | (1,456 | ) | | $ | 610,952 |
| Municipal bonds - taxable | 10,000 |
| | 16 |
| | — |
| | 10,016 |
| Corporate bonds and debt | 393,630 |
| | 87 |
| | (182 | ) | | 393,535 |
| Marketable equity securities | 707 |
| | 2,236 |
| | — |
| | 2,943 |
| Total | $ | 1,016,733 |
| | $ | 2,351 |
| | $ | (1,638 | ) | | $ | 1,017,446 |
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The following is a summary of available-for-sale securities at March 31, 2017 (amounts in thousands): | | | | | | | | | | | | | | | | | | Available-for-sale Securities | | Adjusted Cost | | Gross Unrealized Gains | | Gross Unrealized Losses | | Estimated Fair Value | Government agency bonds | $ | 227,089 |
| | $ | 3 |
| | $ | (227 | ) | | $ | 226,865 |
| Municipal bonds - tax-exempt | 55,289 |
| | — |
| | (10 | ) | | 55,279 |
| Municipal bonds - taxable | 10,000 |
| | 43 |
| | — |
| | 10,043 |
| Corporate bonds and debt | 207,888 |
| | 53 |
| | (169 | ) | | 207,772 |
| Marketable equity securities | 707 |
| | 879 |
| | — |
| | 1,586 |
| Total | $ | 500,973 |
| | $ | 978 |
| | $ | (406 | ) | | $ | 501,545 |
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| Summary of available-for-sale securities in a continuous unrealized loss position |
The following tables show all investments in an unrealized loss position for which an other-than-temporary impairment has not been recognized and the related gross unrealized losses and fair value, aggregated by investment category and the length of time that the individual securities have been in a continuous unrealized loss position (amounts in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | | September 30, 2017 | | Less than 12 Months | | 12 Months or Greater | | Total | | Fair Value | | Unrealized Loss | | Fair Value | | Unrealized Loss | | Fair Value | | Unrealized Loss | Government agency bonds | $ | 596,240 |
| | $ | (1,456 | ) | | $ | — |
| | $ | — |
| | $ | 596,240 |
| | $ | (1,456 | ) | Corporate bonds and debt | 251,785 |
| | (182 | ) | | — |
| | — |
| | 251,785 |
| | (182 | ) | Total | $ | 848,025 |
| | $ | (1,638 | ) | | $ | — |
| | $ | — |
| | $ | 848,025 |
| | $ | (1,638 | ) |
| | | | | | | | | | | | | | | | | | | | | | | | | | March 31, 2017 | | Less than 12 Months | | 12 Months or Greater | | Total | | Fair Value | | Unrealized Loss | | Fair Value | | Unrealized Loss | | Fair Value | | Unrealized Loss | Government agency bonds | $ | 196,875 |
| | $ | (227 | ) | | $ | — |
| | $ | — |
| | $ | 196,875 |
| | $ | (227 | ) | Municipal bonds | 55,279 |
| | (10 | ) | | — |
| | — |
| | 55,279 |
| | (10 | ) | Corporate bonds and debt | 132,820 |
| | (169 | ) | | — |
| | — |
| | 132,820 |
| | (169 | ) | Total | $ | 384,974 |
| | $ | (406 | ) | | $ | — |
| | $ | — |
| | $ | 384,974 |
| | $ | (406 | ) |
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| Summary of investments classified by contractual maturity date |
The amortized cost and estimated fair value of the available-for-sale securities at September 30, 2017, by contractual maturity, excluding marketable equity securities of $2.9 million, which have no contractual maturity, are shown below (amounts in thousands). Expected maturities can differ from contractual maturities because the issuers of the securities may have the right to prepay obligations without prepayment penalties, and the Company views its available-for-sale securities as available for current operations. | | | | | | | | | | | | | | | | | | Adjusted Cost | | Gross Unrealized Gains | | Gross Unrealized Losses | | Estimated Fair Value | Available-for-sale | | | | | | | | Due in one year or less | $ | 397,536 |
| | $ | 2 |
| | $ | (177 | ) | | $ | 397,361 |
| Due after one year and through five years | 618,490 |
| | 113 |
| | (1,461 | ) | | 617,142 |
| Due after five years and through ten years | — |
| | — |
| | — |
| | — |
| Due after ten years | — |
| | — |
| | — |
| | — |
| Total | $ | 1,016,026 |
| | $ | 115 |
| | $ | (1,638 | ) | | $ | 1,014,503 |
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