Stock-based Compensation Share Based Compensation by Payment Award (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended			170 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	545,614	463,604		545,614
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 110.11	$ 126.65		$ 110.11
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	237,359
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 96.23
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	(141,612)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$ 139.82
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(13,737)
Treasury Stock, Shares, Acquired				39,373,745
Treasury Stock, Value, Acquired, Cost Method				$ 1,600,000
Treasury Stock Acquired, Average Cost Per Share				$ 41.20
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period, Weighted Average Grant Date Fair Value	$ 122.47
Share-based Compensation	$ 22,079	$ 21,279	$ 20,470
Restricted Stock Units (RSUs) [Member] | Director Stock Award Program [Member] | Restricted Share Award Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	10,680	8,616	4,536
Share-based Compensation	$ 900	$ 900	$ 900
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	22 months
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 1,300			$ 1,300
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 1,100,000	$ 900,000	$ 900,000
Restricted Stock Units (RSUs) [Member] | Director Stock Award Program [Member] | Total Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,400,000			1,400,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	551,058			551,058
Restricted Stock Units (RSUs) [Member] | Employee stock award program [Member] | Restricted Share Award Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	104,164	91,784	80,983
Share-based Compensation	$ 10,500	$ 10,400	$ 10,500
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	44 months
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 28,600			$ 28,600
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 10,000,000	$ 8,900,000	$ 15,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Intrinsic Value	$ 9,900,000	$ 10,400,000	$ 10,400,000
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ (100)	$ 200	$ 2,900
Restricted Stock Units (RSUs) [Member] | Employee stock award program [Member] | Total Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	11,900,000			11,900,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	1,214,983			1,214,983
Restricted Stock Units (RSUs) [Member] | Performance Share Award Program 2013 Grant [Domain] | Employee stock award program [Member] | Performance Share Award Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(2,200)
Schedule of Share-based Compensation Arrangement by Share-based Payment Award, Performance-Based Units, Vested and Expected to Vest [Table Text Block]	51348
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	$ 1,100
Restricted Stock Units (RSUs) [Member] | Performance Share Award Program 2014 Grant [Domain] | Employee stock award program [Member] | Performance Share Award Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		53,548
Share-based Compensation	$ 3,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 9,000,000
Restricted Stock Units (RSUs) [Member] | Performance Share Award Program 2015 Grant [Domain] | Employee stock award program [Member] | Performance Share Award Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	106,455
Share-based Compensation	$ 3,800
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	12 months
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 11,300,000