Defined Contribution and 401(k) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Defined Contribution and 401(k) (Textual) [Abstract]
Total contribution by employees	$ 0.6	$ 0.5
Retirement Savings Plan under Section 401 (k) [Member]
Additional Defined Contribution And 401(k) (Textual) [Abstract]
Percentage of maximum limit for employees to contribute their cash compensation	100.00%
Percentage of employers matching contribution	100.00%
Percentage of employee contribution	3.00%
Percentage of employee compensation plus matching contribution	50.00%
Percentage of additional employee contribution	2.00%
Total plan expenses	$ 0.7	$ 0.6

The increase in the fair value of plan assets from contributions made by the employer.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(3)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration