Fair Value Measurements - Investments Classified as Available-for-Sale (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Available-for-sale Securities, Balance Sheet, Reported Amounts [Abstract]
Available-for-sale Debt Securities, Amortized Cost	$ 215,607	$ 203,479
Available-for-sale Equity Securities, Amortized Cost	4,424
Available-for-sale Investments, Amortized Cost	220,031
Available for sale Investments, Debt Securities, Gross Unrealized Gain	26	24
Available for sale Investments, Equity Securities, Gross Unrealized Gain	167
Available-for-sale Investments,Unrealized Gross Gain	193
Available for sale Investments, Debt Securities, Gross Unrealized Loss	(24)	(23)
Available for sale Investments, Equity Securities, Gross Unrealized Loss	0
Available-for-sale Investments, Gross Unrealized Loss,	24
Available-for-sale Securities, Debt Securities, Fair Value	215,609	203,480
Available-for-sale Securities, Equity Securities, Fair Value	4,591
Available-for-sale Investments, Fair Value	$ 220,200

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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-Section 50

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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This item represents the cost of debt 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.

+ References

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

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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

+ References

No definition available.

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

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

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

+ References

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

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

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