Pension and Other Post-Retirement Plans (Details 5) (Employee 401(k) Plan, USD $)	1 Months Ended	12 Months Ended
Jan. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee 401(k) Plan
Defined Contribution Plan
Maximum percentage of participant contributions eligible for Employer contribution match, towards defined contribution plan	6.00%	6.00%
Employer's matching contribution on the dollar for the first 6 percent of participant contributions	$ 0.375
Percentage of employer's contribution under 401(k) plan matching up to 6 percent of participant contributions subject to maximum percentage of eligible compensation	2.25%
Contribution expense		$ 1,700,000	$ 1,412,000	$ 1,718,000

The amount of the cost recognized during the period for defined contribution plans.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 11

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

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