Retirement Benefit Plan	12 Months Ended
Dec. 31, 2011
Retirement Benefit Plan [Abstract]
Retirement Benefit Plan	18. Retirement Benefit Plan Our 401(k) retirement plan provides for optional employee contributions up to the Internal Revenue Service limit and discretionary employer matching contributions. We generally make discretionary matching contributions to each participant’s account at a rate of (i) 100% of each participant’s first 1% of contributions plus (ii) 50% of each participant’s contributions up to the next 5% of eligible compensation. We made no discretionary matching contributions from July 1, 2009 through June 30, 2010, but began making them again effective on July 1, 2010. We recorded matching contributions of $8.7 million, $3.9 million and $4.4 million during 2011, 2010 and 2009, respectively.

The entire disclosure for pension and other postretirement benefits.

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