Stock-Based Compensation Plans (Details)	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended		3 Months Ended		3 Months Ended	6 Months Ended
	Jun. 30, 2013 Employee stock option	Jun. 30, 2012 Employee stock option	Jun. 30, 2013 Employee stock option	Jun. 30, 2012 Employee stock option	Jun. 30, 2013 Performance-based restricted stock awards	Jun. 30, 2013 Employee Equity Participation Plan (EEPP) 2013	Jun. 30, 2013 Employee Equity Participation Plan (EEPP) 2013	May 31, 2013 Employee Equity Participation Plan (EEPP) 2013	Jun. 30, 2013 Employee Equity Participation Plan (EEPP) 2013 Stock appreciation rights	May 31, 2013 EEPP 2010	Jun. 30, 2013 EEPP 2010 Stock appreciation rights	Jun. 30, 2013 EEPP Plans prior to 2012 Employee stock option and restricted stock	Jun. 30, 2013 EEPP Plans Beginning 2012 Employee stock option and restricted stock
Stock-Based Compensation Plans
Number of shares counted against the shares available for grant, for each share granted, other than options or SARS						2.09	2.09
The denominator in the conversion factor representing the number of shares that will trigger a decrease in the number of shares available for grant						1	1
Exercise period						10 years	10 years
Pro rata vesting period					3 years							3 years	4 years
Number of shares of common stock initially available for grant								2,800,000
Shares remaining available for option grants or awards						3,500,000	3,500,000			800,000
Stock appreciation rights granted (in shares)									0		0
Weighted average assumptions used to calculate fair value of options granted
Expected stock price volatility (as a percent)	36.00%	38.00%	36.00%	38.00%
Risk free interest rates minimum (as a percent)	0.09%	0.03%	0.09%	0.03%
Risk free interest rates maximum (as a percent)	2.03%	2.01%	2.03%	2.01%
Expected life of options	5 years 4 months 24 days	5 years 2 months 12 days	5 years 4 months 24 days	5 years 2 months 12 days