Equity-based Incentive Plans (Details) (2006 Amended and Restated Equity Incentive Plan (2006 Plan), USD $)		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Stock options	Dec. 31, 2012 Restricted stock units	Dec. 31, 2011 Restricted stock	Dec. 31, 2010 Restricted stock	Dec. 31, 2012 Deferred stock units	Dec. 31, 2011 Deferred stock units
Equity-based Incentive Plans
Original number of shares authorized for issuance		16,000,000
Additional number of shares authorized for issuance		15,500,000
Remaining number of shares available for issuance		14,500,000
Factor used for granting of stock options and stock appreciation rights against the share limit of the awards that are not full value awards	1
Factor used for granting of RSUs, DSUs, restricted and unrestricted stock awards and performance awards against the share limit of the awards that are full value awards	2.09
Vesting percentage		100.00%	100.00%
Vesting period		6 months	2 years
Term of award		5 years
Options exercise price as a percentage of fair value of common stock		100.00%
Eligible age for retirement			59 years 6 months
Number of RSU's
Granted (in shares)			1,422,448	160,000	43,300	79,000	42,000
Vested (in shares)			(143,666)
Forfeited (in shares)			(9,475)
Outstanding at the end of the period (in dollars per share)			1,269,307
Weighted Average Grant Date Fair Value
Granted (in dollars per share)			$ 11.95
Vested (in dollars per share)			$ 12.65
Forfeited (in dollars per share)			$ 11.92
Outstanding, at the end of the period (in dollars per share)			$ 11.87
Aggregate Intrinsic Value
Aggregate Intrinsic Value			$ 17,428,000
Unrecognized Compensation
Unrecognized Compensation			12,318,000
Weighted average remaining life before vesting of the outstanding RSU's			1 year 10 months 24 days
Fair value of vesting during the period			$ 1,800,000
Number of withheld shares			49,000