Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock option activity [Text Block]

	Shares (thousands)		Weighted average exercise price		Weighted average remaining contractual life (in years)	Aggregate intrinsic value (in millions)
Outstanding at January 1, 2016	1,267		$	16.59	0.9	$	33.7
Exercised	(794	)	$	16.07		$	14.4
Outstanding at December 31, 2016	473		$	17.47	0.1	$	10.4
Exercised	(473	)	$	17.47		$	10.4
Outstanding at December 31, 2017	—		$	—	0.0	$	—
Exercised	—		$	—		$	—
Outstanding at December 31, 2018	—		$	—	0.0	$	—
Options exercisable at December 31, 2018	—		$	—	0.0	$	—

Cash Proceeds Received and Tax Benefit from Share-based Payment Awards [Table Text Block]

	Year Ended December 31,
(millions of dollars)	2018		2017		2016
Proceeds from stock options exercised — gross	$	—	$	8.3	$	12.7
Tax benefit	—		8.2		0.3
Proceeds from stock options exercised, net of tax	$	—	$	16.5	$	13.0

Restricted stock compensation expense [Text Block]

	Year Ended December 31,
(millions of dollars, except per share data)	2018		2017		2016
Restricted stock compensation expense	$	25.9	$	27.0	$	26.7
Restricted stock compensation expense, net of tax	$	19.7	$	19.7	$	19.5

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

	Shares subject to restriction (thousands)		Weighted average grant date fair value
Nonvested at January 1, 2016	1,326		$	53.18
Granted	724		$	30.07
Vested	(551	)	$	47.55
Forfeited	(70	)	$	43.05
Nonvested at December 31, 2016	1,429		$	44.12
Granted	804		$	40.10
Vested	(521	)	$	56.53
Forfeited	(119	)	$	38.97
Nonvested at December 31, 2017	1,593		$	38.86
Granted	737		$	51.70
Vested	(556	)	$	42.25
Forfeited	(258	)	$	44.51
Nonvested at December 31, 2018	1,516		$	42.97

Share-based Compensation, Performance Shares Award Nonvested Activity [Table Text Block]

	Number of shares (thousands)		Weighted average grant date fair value
Nonvested at January 1, 2016	475		$	56.55
Granted	171		$	16.61
Forfeited	(236	)	$	49.37
Nonvested at December 31, 2016	410		$	43.99
Granted	201		$	45.57
Forfeited	(256	)	$	61.40
Nonvested at December 31, 2017	355		$	32.35
Granted	287		$	68.38
Forfeited	(345	)	$	38.26
Nonvested at December 31, 2018	297		$	60.35

	Year Ended December 31,
(millions of dollars, except share data)	2018		2017		2016
Expense	$	18.0	$	15.9	$	7.1
Number of shares	249,000		126,000		—

A summary of the status of the Company’s nonvested relative revenue growth performance shares at December 31, 2018, 2017 and 2016 is as follows:

	Number of shares (thousands)		Weighted average grant date fair value
Nonvested at January 1, 2016	—		$	—
Granted	485		$	38.62
Vested	(126	)	$	38.62
Forfeited	(39	)	$	38.62
Nonvested at December 31, 2016	320		$	38.62
Granted	198		$	40.08
Vested	(156	)	$	38.62
Forfeited	(7	)	$	39.20
Nonvested at December 31, 2017	355		$	39.42
Granted	287		$	50.82
Vested	(166	)	$	38.62
Forfeited	(179	)	$	45.82
Nonvested at December 31, 2018	297		$	47.03

	Year Ended December 31,
(millions of dollars, except share data)	2018		2017		2016
Expense	$	9.0	$	9.9	$	9.6
Number of shares	—		—		—