Share-Based Compensation Level 4 (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total pretax employee share-based compensation expense included in net income	$ 14,788,000	$ 14,056,000	$ 13,843,000
Income tax benefit related to share-based compensation included in net income	$ 5,416,000	$ 6,427,000	$ 5,068,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Exercised	0	0	(122,000)
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options				9,520,299
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	4 years 7 months 6 days
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Exercise Price, Beginning Balance				$ 19.77
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options				6,190,827
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price				$ 16.64
Stock Option Plan Exercise Range 1 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 5.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 10.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options				725,074
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	1 year 1 month 6 days
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Exercise Price, Beginning Balance				$ 9.09
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options				725,074
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price				$ 9.09
Stock Option Plan Exercise Range 2 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 10.01
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 15.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options				938,630
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	2 years 1 month 6 days
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Exercise Price, Beginning Balance				$ 11.18
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options				938,630
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price				$ 11.18
Stock Option Plan Exercise Range 3 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 15.01
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 20.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options				2,757,306
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	3 years 8 months 12 days
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Exercise Price, Beginning Balance				$ 16.56
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options				2,757,306
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price				$ 16.56
Stock Option Plan Exercise Range 4 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit	$ 20.01
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit	$ 25.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options				3,580,379
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	5 years 7 months 6 days
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Exercise Price, Beginning Balance				$ 22.63
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options				1,769,817
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price				$ 22.75
Stock Option Plan Exercise Range 5 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options				1,518,910
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	7 years 1 month 6 days
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Exercise Price, Beginning Balance				$ 29.25
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options				0
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price				$ 0.00
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	2.00%	2.00%	1.80%
Expected volatility	19.00%	19.70%	23.30%
Risk-free interest rate	1.60%	1.00%	1.30%
Expected holding period	4 years	4 years	4 years
Total pretax employee share-based compensation expense included in net income	$ 6,900,000	$ 7,600,000	$ 7,900,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding at beginning of period	10,775,136
Options outstanding at beginning of period, weighted average exercise price	$ 16.49
Granted	1,524,860
Granted, Weighted Average Exercise Price	$ 29.25
Exercised	(2,759,309)
Exercised, Weighted Average Exercise Price	$ 12.18
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	(20,388)
Cancelled, Weighted Average Exercise Price	$ 24.59
Options outstanding at end of period	9,520,299	10,775,136
Options outstanding at end of period, weighted average exercise price	$ 19.77	$ 16.49
Options exercisable at December 31, 2011	10,775,136	10,775,136		9,520,299
Options exercisable at December 31, 2011, Weighted Average Exercise Price	$ 16.49	$ 16.49		$ 19.77
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number				6,190,827
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price				$ 16.64
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total pretax employee share-based compensation expense included in net income	$ 5,600,000	$ 5,600,000	$ 5,900,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested restricted shares at beginning of period	500,744
Nonvested restricted shares at beginning of period, weighted average grant date fair value	$ 21.48
Granted	208,933
Granted, Weighted Average Grant Date Fair Value	$ 29.28	$ 22.28	$ 23.00
Vested	(265,733)
Vested, Weighted Average Grant Date Fair Value	$ 20.56
Nonvested restricted shares at end of period	441,811	500,744
Nonvested restricted shares at end of period, weighted average grant date fair value	$ 25.70	$ 21.48
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	$ 5,500,000	$ 5,700,000	$ 6,300,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(2,133)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 25.04
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested	$ 4,500,000	3,200,000	$ 4,900,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total pretax employee share-based compensation expense included in net income	$ 2,000,000	$ 800,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested restricted shares at beginning of period	123,510
Nonvested restricted shares at beginning of period, weighted average grant date fair value	$ 25.72
Granted	95,780
Granted, Weighted Average Grant Date Fair Value	$ 27.94	$ 25.72
Vested	(48,136)
Vested, Weighted Average Grant Date Fair Value	$ 25.86
Nonvested restricted shares at end of period	167,030	123,510
Nonvested restricted shares at end of period, weighted average grant date fair value	$ 26.92	$ 25.72
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	$ 1,200,000	$ 50,200
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(4,124)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 27.01
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested	$ 600,000	$ 0