Exit of Joint Venture (Details) (USD $)	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Audco [Member]	Mar. 28, 2013 Audco [Member]
Schedule of Equity Method Investments [Line Items]
Percentage acquired				100.00%
Ownership percentage				50.00%
Percentage ownership sold				50.00%
Proceeds from sale of equity method investment	$ 46,240,000	$ (1,620,000)	$ 46,240,000
Cash payment for acquisition of equity method investment	10,143,000	3,996,000	10,143,000
Assets			25,000,000
Remeasurement gain	15,315,000	0	15,315,000
Gain on sale of equity method investment affiliate	$ 12,995,000	$ 0	$ 12,995,000

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References+ Details

The amount of assets reported by an equity method investment of the entity.

+ References

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

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Section S99

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

-Paragraph 18

-Subparagraph f

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

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-Article 1

+ Details

- Definition

The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ References+ Details