Cash, Cash Equivalents, and Investments - Summary of Cash, Cash Equivalents and Held-to-Maturity Investments by Type (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	$ 63,395	$ 37,808
Gross Unrealized Gains	16
Gross Unrealized Losses	(14)	(1)
Fair Value	63,397	37,807
Cash and Money Market Funds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	42,226	36,127
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	42,226	36,127
State and Municipal Obligations [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	10,807
Gross Unrealized Gains	14
Gross Unrealized Losses
Fair Value	10,821
Corporate Bonds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	7,743	1
Gross Unrealized Gains	2
Gross Unrealized Losses	(14)
Fair Value	7,731	1
Certificates of Deposit [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	2,619	1,680
Gross Unrealized Gains
Gross Unrealized Losses		(1)
Fair Value	$ 2,619	$ 1,679