Income Taxes - Schedule of Unrecognized Tax Benefits (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning of the Period Balance	$ 7,974us-gaap_UnrecognizedTaxBenefits	$ 6,915us-gaap_UnrecognizedTaxBenefits	$ 5,796us-gaap_UnrecognizedTaxBenefits
Increases related to tax positions taken during a prior period	63	406	43
Increases related to tax positions related to MTS			1,066
Decreases related to tax positions taken during the prior period	(89)	(79)	0
Increases related to tax positions taken during the current period	801	764	422
Decreases related to settlements	0	0	(33)
Decreases related to expiration of statute of limitations	(264)	(32)	(379)
End of the Period Balance	$ 8,485us-gaap_UnrecognizedTaxBenefits	$ 7,974us-gaap_UnrecognizedTaxBenefits	$ 6,915us-gaap_UnrecognizedTaxBenefits

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Unrecognized Tax Benefit

-URI http://asc.fasb.org/extlink&oid=6527854

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-Publisher FASB

-Name Accounting Standards Codification

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-Section 50

-Paragraph 15A

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

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-Paragraph 15A

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

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Amount of increase in unrecognized tax benefits resulting from acquisitions.

+ References

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

+ References

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-Name Accounting Standards Codification

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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-Name Accounting Standards Codification

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