Share-Based Compensation Expense (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Performance Based Compensation Expense Issuable in Stock or Cash		$ 2,000,000
Excess Tax Benefits from Stock Option Exercises		200,000	300,000	1,200,000
Cash Received from Employees for Stock Purchases		3,300,000	2,300,000	3,500,000
Employee Stock Purchase Plan Compensation Expense		200,000
ESPP Percent of Market Price Purchased At		90.00%
Employee Service Share Based Compensation Tax Benefit From Compensation Expense, Effective Rate		42.00%
Common Stock Market Price		11.16
Total compensation cost related to the outstanding or unvested restricted stock and restricted stock units		12,500,000
Share-based compensation - incremental compensation cost on modification	400,000
Number of Shares, Stock options, Grants		144,000
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		4,300,000	3,700,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans		198,956	189,813	146,876
Shares Held in Employee Stock Option Plan, Allocated		1,000,000
Restricted Stock Units (RSU's) Performance Based Vesting [Member]
Restricted Stock Units, Grants		175,973
Restricted Stock Awards, Grants Fair Value		2,200,000
Restricted stock and restricted stock units [Member]
Weighted Average remaining vesting period		two
Total compensation cost related to the outstanding or unvested restricted stock and restricted stock units		11,400,000
Restricted Stock - Vest Performance Based [Member]
Vesting period	7 years	3 years
Stock Options [Member]
Intrinsic Value, Options Exercisable		100,000
Intrinsic Value, Options Outstanding		200,000
Restricted Stock [Member]
Median Price, Outstanding, Period End		12.85
Restricted Stock Units (RSUs) [Member]
Median Price, Outstanding, Period End		13.75
Restricted Stock Units, Grants		618,991
Restricted Stock Awards, Grants Fair Value		$ 8,100,000
Unvested Stock-Based Awards [Member]
Vesting period		2 years