Share-Based Payments (Details 6) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Assumptions used in valuation of market based stock units
Expected dividend yield	0.00%		0.00%	0.00%
Range of expected stock price volatility	0.00%		0.00%	30.80%
Market stock units
Assumptions used in valuation of market based stock units
Expected dividend yield	0.00%		0.00%
Minimum range of risk-free interest rates	0.20%		0.30%
Maximum range of risk-free interest rates	0.60%		1.90%
60 calendar day average stock price on grant date minimum	113.83		66.78
60 calendar day average stock price on grant date maximum	149.79		101.16
Weighted average grant date fair value	134.95	[1]	74.19
Market stock units | Maximum
Assumptions used in valuation of market based stock units
Range of expected stock price volatility	34.00%		33.40%
Market stock units | Minimum
Assumptions used in valuation of market based stock units
Range of expected stock price volatility	29.60%		25.70%

[1] MSUs granted in 2012 include approximately 39,000 and 42,000 MSUs issued in 2012 based upon the attainment of performance criteria set for 2011 and 2010, respectively, in relation to shares granted in those years. The remainder of MSUs granted during 2012 include awards granted in conjunction with our annual awards made in February 2012 and MSUs granted in conjunction with the hiring of employees. These grants reflect the target number of shares eligible to be earned at the time of grant.