Retirement benefits (Tables)
 9 Months Ended
Sep. 30, 2018
Retirement Benefits [Abstract]  
Schedule of Net Benefit Costs
The components of net periodic pension cost for our pension plans were as follows:
 
U.S. Plans
 
Non-U.S. Plans
 
Total
(In millions)
2018
 
2017
 
2018
 
2017
 
2018
 
2017
 
 
 
 
 
 
 
 
 
 
 
 
Three months ended September 30,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Service cost
$
—

 
—

 
2.6

 
2.8

 
2.6

 
2.8

Interest cost on projected benefit obligation
8.0

 
8.8

 
2.5

 
3.2

 
10.5

 
12.0

Return on assets – expected
(13.4
)
 
(13.3
)
 
(2.7
)
 
(2.6
)
 
(16.1
)
 
(15.9
)
Amortization of losses
6.8

 
6.3

 
1.0

 
1.4

 
7.8

 
7.7

Amortization of prior service cost
—

 
—

 
—

 
0.4

 
—

 
0.4

Settlement loss
—

 
—

 
0.4

 
0.6

 
0.4

 
0.6

Net periodic pension cost
$
1.4

 
1.8

 
3.8

 
5.8

 
5.2

 
7.6

 
 
 
 
 
 
 
 
 
 
 
 
Nine months ended September 30,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Service cost
$
—

 
—

 
8.2

 
8.5

 
8.2

 
8.5

Interest cost on projected benefit obligation
24.0

 
26.4

 
9.8

 
12.3

 
33.8

 
38.7

Return on assets – expected
(40.2
)
 
(39.9
)
 
(8.4
)
 
(7.4
)
 
(48.6
)
 
(47.3
)
Amortization of losses
20.8

 
18.7

 
3.3

 
4.0

 
24.1

 
22.7

Amortization of prior service cost
—

 
—

 
0.2

 
0.8

 
0.2

 
0.8

Settlement loss
—

 
—

 
1.4

 
1.4

 
1.4

 
1.4

Net periodic pension cost
$
4.6

 
5.2

 
14.5

 
19.6

 
19.1

 
24.8
Schedule of Costs of Retirement Plans
The components of net periodic postretirement cost related to retirement benefits other than pensions were as follows:
 
UMWA Plans
 
Black Lung and Other Plans
 
Total
(In millions)
2018
 
2017
 
2018
 
2017
 
2018
 
2017
 
 
 
 
 
 
 
 
 
 
 
 
Three months ended September 30,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Interest cost on accumulated postretirement benefit obligations
$
4.2

 
4.6

 
0.7

 
0.9

 
4.9

 
5.5

Return on assets – expected
(4.1
)
 
(4.1
)
 
—

 
—

 
(4.1
)
 
(4.1
)
Amortization of losses
4.9

 
5.2

 
1.6

 
1.0

 
6.5

 
6.2

Amortization of prior service (credit) cost
(1.2
)
 
(1.2
)
 
0.2

 
0.5

 
(1.0
)
 
(0.7
)
Net periodic postretirement cost
$
3.8

 
4.5

 
2.5

 
2.4

 
6.3

 
6.9

 
 
 
 
 
 
 
 
 
 
 
 
Nine months ended September 30,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Service cost
$
—

 
—

 
0.1

 
0.1

 
0.1

 
0.1

Interest cost on accumulated postretirement benefit obligations
12.9

 
13.7

 
2.3

 
2.4

 
15.2

 
16.1

Return on assets – expected
(12.5
)
 
(12.4
)
 
—

 
—

 
(12.5
)
 
(12.4
)
Amortization of losses
15.4

 
14.6

 
4.3

 
3.0

 
19.7

 
17.6

Amortization of prior service (credit) cost
(3.5
)
 
(3.5
)
 
0.8

 
1.3

 
(2.7
)
 
(2.2
)
Net periodic postretirement cost
$
12.3

 
12.4

 
7.5

 
6.8

 
19.8

 
19.2