Employee and Non Employee Director Stock and Benefit Plans (Details 6) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Retirement Savings Plan (RSP)
Employee and Non Employee Director Benefit Plans
In accordance with the Internal Revenue Code, the maximum annual eligible compensation under the plan, prior to January 1, 2011		$ 245,000
Company guaranteed contribution, under the plan, prior to January 1, 2011 (as a percent)			3.00%
Company matching contribution, under the plan, prior to January 1, 2011 (as a percent)			66.667%
Maximum eligible compensation (as a percent)	4.00%	6.00%
Company matching contribution, under the plan, effective January 1, 2012 (as a percent)	50.00%	50.00%
Benefit costs		6,600,000	10,200,000	10,800,000
Retirement Savings Plan (RSP) | Minimum
Employee and Non Employee Director Benefit Plans
Company discretionary contribution prior to January 1, 2011, based on profits (as a percent)			0.00%
Retirement Savings Plan (RSP) | Maximum
Employee and Non Employee Director Benefit Plans
Company discretionary contribution prior to January 1, 2011, based on profits (as a percent)			8.00%
Directors' Retainer Fee Subplan
Employee and Non Employee Director Benefit Plans
Benefit costs		769,000	647,000	716,000
Annual retainer fee received by the lead director and chairman, since 2006 and until August 2008		90,000
Annual retainer fee received by lead director and chairman since August, 2008		160,000
Annual retainer fee received by non-employee directors, excluding the lead director and chairman, since 2006		$ 60,000
Deferred shares or units received		29,347	16,819	13,699