Fair Value Measurement - Summary of Marketable Securities Consist of Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Recorded Basis	$ 6,048	$ 20,930
Recorded Basis	0	29,957
Current Available-for-Sale [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cost	0	30,000
Gross Unrealized Gains (Losses)	0	(43)
Recorded Basis	0	29,957
Long-Term Available-for-Sale [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cost	6,045	20,940
Gross Unrealized Gains (Losses)	3	(10)
Recorded Basis	6,048	20,930
Municipal Bonds [Member] \| Long-Term Available-for-Sale [Member] \| Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cost	3,438	3,843
Gross Unrealized Gains (Losses)	6	7
Recorded Basis	3,444	3,850
Corporate Bonds [Member] \| Long-Term Available-for-Sale [Member] \| Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cost	2,607	2,153
Gross Unrealized Gains (Losses)	(3)	(3)
Recorded Basis	2,604	2,150
Variable Rate Demand Notes (VRDN) [Member] \| Current Available-for-Sale [Member] \| Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cost	0	21,670
Gross Unrealized Gains (Losses)	0	0
Recorded Basis	0	21,670
Certificate of Deposit [Member] \| Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cost	0	14,944
Gross Unrealized Gains (Losses)	0	(14)
Recorded Basis	0	14,930
Certificate of Deposit [Member] \| Current Available-for-Sale [Member] \| Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cost	0	8,330
Gross Unrealized Gains (Losses)	0	(43)
Recorded Basis	$ 0	$ 8,287

Marketable securities unrealized holding gain loss.

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Amount before tax of unrealized gain (loss) in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

No definition available.

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- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount of debt securities categorized neither as held-to-maturity nor trading.

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Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

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Total debt and equity financial instruments including: (1) securities held-to-maturity and (2) securities available-for-sale that will be held for the long-term.

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