Cash, Cash Equivalents, and Investments - Summary of Cash, Cash Equivalents and Held-to-Maturity Investments by Type (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	$ 77,507	$ 63,395
Gross Unrealized Gains	29	16
Gross Unrealized Losses	(19)	(14)
Fair Value	77,517	63,397
Cash and Money Market Funds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	44,897	42,226
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	44,897	42,226
State and Municipal Obligations [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	15,213	10,807
Gross Unrealized Gains	24	14
Gross Unrealized Losses
Fair Value	15,237	10,821
Corporate Bonds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	14,781	7,743
Gross Unrealized Gains	5	2
Gross Unrealized Losses	(19)	(14)
Fair Value	14,767	7,731
Certificates of Deposit [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	2,616	2,619
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	$ 2,616	$ 2,619

- Definition

Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

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