Stock Options and SARs (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	54,000	32,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 36.68	$ 33.98
Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options	$ 6	$ 13	$ 2
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	3	$ 4	$ 1
Unrecognized compensation expense	$ 9
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 103.66	$ 84.58	$ 74.55
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Exercised	(71,494)	(160,408)	(36,599)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options	63,000
Price Range One [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options	2,000
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	6 years 2 months 3 days
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Exercise Price, Beginning Balance	$ 53.57
Price Range Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options	8,000
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	5 years 2 months 13 days
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Exercise Price, Beginning Balance	$ 77.99
Price Range Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options	53,000
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	6 years 4 months 15 days
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Exercise Price, Beginning Balance	$ 102.62
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 0
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	1 year 6 months
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 36.63	$ 33.98
Expected Term	4 years 4 months 28 days	5 years	4 years 5 months 11 days
Expected volatility	37.19%	43.61%	42.14%
Risk-free interest rate	1.63%	1.72%	1.51%
Expected dividend yield	0.00%	0.00%	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested at beginning of period	46,000	76,000	98,000
Granted	9,000	11,000
Exercised	(38,000)	(40,000)	(3,000)
Forfeited	(2,000)	(1,000)	(19,000)
Non-vested at end of period	15,000	46,000	76,000
Non-vested SARS Weighted Average Exercise Price	$ 86.35	$ 70.46	$ 69.06	$ 68.36
Granted SARS Weighted Average Exercise Price	101.58	84.67
Exercised SARs Weighted Average Exercise Price	69.81	71.15	61.42
Forfeited or expired SARs Weighted Average Exercise Price	$ 98.46	$ 76.28	$ 66.80
Share-based Compensation Arangements by Share-Payment Award, Equity Awards other than options, excercisable, number	8,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Awards other than Options, Exerciable, Weighted-Average Exercisable Price	$ 72.76
Stock Appreciation Rights (SARs) [Member] | Employee Benefits [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Share-based Arrangements, Liability, Classified, Noncurrent		$ 1
Stock Appreciation Rights (SARs) [Member] | Accrued Employee Liabilities [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Share-based Arrangements, Liability, Current		$ 1
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based Compensation vesting increments	one-third
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Unrecognized compensation expense	$ 1
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	1 year
Expected Term	5 years	5 years
Expected volatility	38.19%	43.61%
Risk-free interest rate	1.60%	1.72%
Expected dividend yield	0.00%	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding Options Beginning Period	74,000	206,000	362,000
Granted	54,000	32,000
Exercised	(71,000)	(160,000)	(36,000)
Forfeited or expired	(9,000)	(4,000)	(120,000)
Outstanding Options Ending Period	48,000	74,000	206,000
Outstanding Options Weighted Average Exercise Price	$ 101.40	$ 71.22	$ 68.74	$ 67.13
Granted Options Weighted Average Exercise Price	102.59	84.67
Exercised Options Weighted Average Exercise Price	71.12	70.88	55.88
Forfeited or expired Options Weighted Average Exercise Price	$ 101.58	$ 66.75	$ 67.81
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	2,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 74.29
Maximum [Member] | Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Date	10 years
Unrecognized compensation expense	$ 1
Maximum [Member] | Stock Appreciation Rights (SARs) [Member] | Employee Benefits [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Share-based Arrangements, Liability, Classified, Noncurrent	1
Maximum [Member] | Stock Appreciation Rights (SARs) [Member] | Accrued Employee Liabilities [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Share-based Arrangements, Liability, Current	$ 1
Maximum [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Date	10 years
Minimum [Member] | Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Date	7 years
Minimum [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Date	7 years