INCOME TAXES (Tables)
 6 Months Ended
Jun. 30, 2017
Income Tax Disclosure [Abstract]  
Effective Tax Rate Reconciliation (Percent)
The following table accounts for the difference between the actual tax provision and the amounts obtained by applying the statutory U.S. federal income tax rate of 35.0% to income before taxes.

 
Three Months Ended
June 30,
 
Six Months Ended
June 30,
Effective Tax Rate Reconciliation (Percent)
2017
 
2016
 
2017
 
2016
Statutory federal tax rate
35.0
 %
 
35.0
 %
 
35.0
 %
 
35.0
 %
Salt depletion
(9.6
)
 
40.1

 
(10.2
)
 
9.6

Stock-based compensation
3.9

 
—

 
61.0

 
—

Foreign rate differential
(3.2
)
 
14.0

 
(3.7
)
 
1.5

U.S. tax on foreign earnings
3.2

 
(13.7
)
 
3.7

 
(1.4
)
Dividends paid to CEOP
(0.4
)
 
3.4

 
(0.4
)
 
0.6

State income taxes, net
0.4

 
21.8

 
(0.3
)
 
5.6

Change in valuation allowance
—

 
(1.0
)
 
—

 
(0.3
)
Change in tax contingencies
45.7

 
(20.6
)
 
251.3

 
(5.1
)
Return to provision
(2.3
)
 
18.9

 
(42.6
)
 
5.7

Other, net
0.2

 
(2.1
)
 
(1.5
)
 
(0.4
)
Effective tax rate
72.9
 %
 
95.8
 %
 
292.3
 %
 
50.8
 %
Unrecognized Tax Benefits
The amount of unrecognized tax benefits was as follows:
 
June 30,
 
2017
 
2016
 
($ in millions)
Balance at beginning of year
$
38.4

 
$
35.1

Increases for prior year tax positions
4.9

 
5.7

Decreases for prior year tax positions
(9.2
)
 
(1.8
)
Increases for current year tax positions
1.4

 
0.9

Settlement with taxing authorities
(1.0
)
 
(2.1
)
Reductions due to statute of limitations
(0.2
)
 
(0.3
)
Balance at end of period
$
34.3

 
$
37.5
Tax Returns Subject to Examination
For our primary tax jurisdictions, the tax years that remain subject to examination are as follows:

 
Tax Years
U.S. federal income tax
2013 - 2016
U.S. state income tax
2006 - 2016
Canadian federal income tax
2012 - 2016
Brazil
2014 - 2016
Germany
2015 - 2016
China
2014 - 2016
The Netherlands
2014 - 2016
South Korea
2014 - 2016