Stock-Based Compensation (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) plan $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares	Jan. 18, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based compensation plans covering employees, officers and directors | plan	4
Expiration period of stock options (in years)	10 years
Fair value assumptions of stock options using Black-Scholes option pricing model
Weighted average expected life of options, maximum (in years)		4 years	4 years
Stock Option, Intrinsic Value
Stock Issued During Period, Shares, Share-based Compensation, Gross	0
Weighted average grant date fair value of options (in dollars per share) | $ / shares		$ 5.23	$ 4.73
Employee Benefit Plan
Maximum 401(K) plan contribution by employer as a percent of employee's salary	3.50%
Aggregate employer 401(K) plan contribution during the period | $	$ 1,500,000	$ 1,400,000	$ 1,300,000
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance	2,900,000
Number of shares authorized for issuance	3,000,000.0
Nonvested Restricted Stock and Restricted Stock Units, Weighted Average Grant Date Fair Value
Number of shares purchased	100,000
Employee Stock | Employee
Nonvested Restricted Stock and Restricted Stock Units, Weighted Average Grant Date Fair Value
Discount related to the Employee Stock Purchase Plan	90.00%
Employee Stock | Director
Nonvested Restricted Stock and Restricted Stock Units, Weighted Average Grant Date Fair Value
Discount related to the Employee Stock Purchase Plan	95.00%
Stock Options
Fair value assumptions of stock options using Black-Scholes option pricing model
Risk-free interest rate, minimum	1.69%	0.93%	1.02%
Risk-free interest rate, maximum	1.87%	1.27%	1.38%
Dividend yield		6.00%	5.50%
Volatility factors of the expected market price for our common stock, minimum rate	21.50%	19.10%	19.00%
Volatility factors of the expected market price for our common stock, maximum rate	21.60%	20.60%	20.00%
Stock Option, Shares
Outstanding at the beginning of the period (in shares)	5,025,000
Granted (in shares)	0
Options exercised (in shares)	(201,000)
Options forfeited (in shares)	(35,000)
Options exercised (in shares)	(5,000)
Outstanding at the end of the period (in shares)	4,784,000	5,025,000
Exercisable at the end of the period (in shares)	4,196,000
Stock Option, Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 58.57
Options granted (in dollars per share) | $ / shares	0
Options exercised (in dollars per share) | $ / shares	58.93
Options exercised (in dollars per share) | $ / shares	43.53
Options forfeited (in dollars per share) | $ / shares	59.49
Outstanding at the end of the period (in dollars per share) | $ / shares	59.20	$ 58.57
Exercisable at the end of the period (in dollars per share) | $ / shares	$ 58.89
Stock Option, Weighted Average Remaining Contractual Life (years)
Outstanding at the end of the period (in years)	6 years 4 months 24 days
Exercisable at the end of the period (in years)	6 years 3 months 18 days
Stock Option, Intrinsic Value
Outstanding at the end of the period | $	$ 13,566,000
Exercisable at the end of the period | $	13,521,000
Unrecognized compensation cost related to nonvested awards | $	$ 300,000
Weighted average period over which cost is recognized (in years)	1 year
Proceeds from options exercised | $	$ 8,800,000	$ 16,300,000	$ 20,400,000
Intrinsic value for options exercised | $	3,100,000	7,000,000.0	8,000,000.0
Deferred income tax expense (benefit) | $	0
Stock Options | General and administrative expenses
Stock Option, Intrinsic Value
Compensation cost | $	2,600,000	4,800,000	6,200,000
Restricted Stock or Restricted Stock Units
Stock Option, Intrinsic Value
Unrecognized compensation cost related to nonvested awards | $	$ 22,000,000.0
Weighted average period over which cost is recognized (in years)	1 year 5 months 19 days
Nonvested Restricted Stock and Restricted Stock Units, Weighted Average Grant Date Fair Value
Intrinsic value for options vested during period | $	$ 15,500,000	16,600,000	13,900,000
Restricted Stock or Restricted Stock Units | General and administrative expenses
Stock Option, Intrinsic Value
Compensation cost | $	$ 27,300,000	$ 21,700,000	$ 14,700,000
Restricted Stock
Nonvested Restricted Stock and Restricted Stock Units, Shares
Nonvested at the beginning of the period (in shares)	319,000
Granted (in shares)	161,000
Vested (in shares)	(182,000)
Forfeited (in shares)	(22,000)
Nonvested at the end of the period (in shares)	276,000	319,000
Nonvested Restricted Stock and Restricted Stock Units, Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share) | $ / shares	$ 58.36
Granted (in dollars per share) | $ / shares	50.77
Vested (in dollars per share) | $ / shares	59.35
Forfeited (in dollars per share) | $ / shares	53.94
Nonvested at the end of the period (in dollars per share) | $ / shares	$ 53.64	$ 58.36
Restricted Stock Units
Nonvested Restricted Stock and Restricted Stock Units, Shares
Nonvested at the beginning of the period (in shares)	414,000
Granted (in shares)	331,000
Vested (in shares)	(104,000)
Forfeited (in shares)	(14,000)
Nonvested at the end of the period (in shares)	627,000	414,000
Nonvested Restricted Stock and Restricted Stock Units, Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share) | $ / shares	$ 62.01
Granted (in dollars per share) | $ / shares	53.44
Vested (in dollars per share) | $ / shares	61.47
Forfeited (in dollars per share) | $ / shares	58.29
Nonvested at the end of the period (in dollars per share) | $ / shares	$ 57.70	$ 62.01
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	2 years
Minimum | Restricted Stock or Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	2 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	3 years
Maximum | Restricted Stock or Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	5 years
2006 Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance	0
2012 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance	3,600,000
Number of shares authorized for issuance	10,500,000
2017 LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Previous discretionary goal				50.00%
2017 LTIP | Performance Based RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocation of awards				60.00%
2017 LTIP | Time Based RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocation of awards				40.00%
Executive Deferred Stock Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based compensation plans for executive officers | plan	1
Number of shares available for future issuance	600,000
Number of shares authorized for issuance	600,000
Nonemployee Directors' Deferred Stock Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based compensation plans for directors | plan	1
Number of shares available for future issuance	400,000
Number of shares authorized for issuance	600,000