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Fair Value Measurements (Detail) - Fair Value Measurements at Reporting Date Using - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Investment Securities	$ 1,090,057	$ 672,463
Short-term investments
Investment Securities	819,477	532,477
Long-term investments
Investment Securities	2,231	0
Fair Value, Inputs, Level 1
Investment Securities	25,019	5,340
Fair Value, Inputs, Level 1 | Short-term investments
Investment Securities	0	0
Fair Value, Inputs, Level 1 | Long-term investments
Investment Securities	0	0
Fair Value, Inputs, Level 2
Investment Securities	1,065,038	667,123
Fair Value, Inputs, Level 2 | Short-term investments
Investment Securities	819,477	532,477
Fair Value, Inputs, Level 2 | Long-term investments
Investment Securities	2,231	0
Commercial paper | Short-term investments
Investment Securities	419,469	229,821
Commercial paper | Fair Value, Inputs, Level 1 | Short-term investments
Investment Securities	0	0
Commercial paper | Fair Value, Inputs, Level 2 | Short-term investments
Investment Securities	419,469	229,821
US Government Corporations and Agencies Securities | Short-term investments
Investment Securities	0	48,598
US Government Corporations and Agencies Securities | Fair Value, Inputs, Level 1 | Short-term investments
Investment Securities	0	0
US Government Corporations and Agencies Securities | Fair Value, Inputs, Level 2 | Short-term investments
Investment Securities	0	48,598
Municipal debt securities | Short-term investments
Investment Securities	165,572	87,290
Municipal debt securities | Long-term investments
Investment Securities	2,231	0
Municipal debt securities | Fair Value, Inputs, Level 1 | Short-term investments
Investment Securities	0	0
Municipal debt securities | Fair Value, Inputs, Level 1 | Long-term investments
Investment Securities	0	0
Municipal debt securities | Fair Value, Inputs, Level 2 | Short-term investments
Investment Securities	165,572	87,290
Municipal debt securities | Fair Value, Inputs, Level 2 | Long-term investments
Investment Securities	2,231	0
Corporate debt securities | Short-term investments
Investment Securities	234,436	166,768
Corporate debt securities | Fair Value, Inputs, Level 1 | Short-term investments
Investment Securities	0	0
Corporate debt securities | Fair Value, Inputs, Level 2 | Short-term investments
Investment Securities	234,436	166,768
Cash Equivalents
Cash Equivalents	268,349	139,986
Cash Equivalents | Fair Value, Inputs, Level 1
Cash Equivalents	25,019	5,340
Cash Equivalents | Fair Value, Inputs, Level 2
Cash Equivalents	243,330	134,646
Cash Equivalents | Money market funds
Cash Equivalents	25,019	5,340
Cash Equivalents | Money market funds | Fair Value, Inputs, Level 1
Cash Equivalents	25,019	5,340
Cash Equivalents | Money market funds | Fair Value, Inputs, Level 2
Cash Equivalents	0	0
Cash Equivalents | Commercial paper
Cash Equivalents	179,455	48,908
Cash Equivalents | Commercial paper | Fair Value, Inputs, Level 1
Cash Equivalents	0	0
Cash Equivalents | Commercial paper | Fair Value, Inputs, Level 2
Cash Equivalents	179,455	48,908
Cash Equivalents | US Government Corporations and Agencies Securities
Cash Equivalents	0	51,400
Cash Equivalents | US Government Corporations and Agencies Securities | Fair Value, Inputs, Level 1
Cash Equivalents	0	0
Cash Equivalents | US Government Corporations and Agencies Securities | Fair Value, Inputs, Level 2
Cash Equivalents	0	51,400
Cash Equivalents | Municipal debt securities
Cash Equivalents	63,875	34,338
Cash Equivalents | Municipal debt securities | Fair Value, Inputs, Level 1
Cash Equivalents	0	0
Cash Equivalents | Municipal debt securities | Fair Value, Inputs, Level 2
Cash Equivalents	$ 63,875	$ 34,338

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value portion 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.

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