Pension plans 4 (Details) - USD ($) $ in Millions | 12 Months Ended |
Dec. 31, 2015 | Dec. 31, 2014 |
General insurance account [Member] | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | $ 5.5 | $ 17.6 |
Actual return on plan assets | 0.3 | (0.8) |
Purchases, sales and settlments, net | 0 | (0.2) |
Defined Benefit Plan, Divestitures, Plan Assets | | (9.9) |
Foreign currency exchange rates | (0.5) | (1.2) |
Fair value of plan assets at the end of the year | 5.3 | 5.5 |
U.S. Pension Plans [Member] | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 685.7 | 627.2 |
Actual return on plan assets | (11.6) | 88.6 |
Defined Benefit Plan, Divestitures, Plan Assets | 0 | 0 |
Foreign currency exchange rates | 0 | 0 |
Fair value of plan assets at the end of the year | 641.3 | 685.7 |
U.S. Pension Plans [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 169.7 | |
Fair value of plan assets at the end of the year | 183.8 | 169.7 |
U.S. Pension Plans [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 516 | |
Fair value of plan assets at the end of the year | 457.5 | 516 |
U.S. Pension Plans [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 12.8 | |
Fair value of plan assets at the end of the year | 18.8 | 12.8 |
U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 6.7 | |
Fair value of plan assets at the end of the year | 8.8 | 6.7 |
U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 243.6 | |
Fair value of plan assets at the end of the year | 235.5 | 243.6 |
U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 1.1 | |
Fair value of plan assets at the end of the year | 2.5 | 1.1 |
U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 48.6 | |
Fair value of plan assets at the end of the year | 42 | 48.6 |
U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 144.7 | |
Fair value of plan assets at the end of the year | 151.9 | 144.7 |
U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 15.6 | |
Fair value of plan assets at the end of the year | 16.2 | 15.6 |
U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 11.1 | |
Fair value of plan assets at the end of the year | 10.6 | 11.1 |
U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 151.1 | |
Fair value of plan assets at the end of the year | 144.9 | 151.1 |
U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 50.4 | |
Fair value of plan assets at the end of the year | 10.1 | 50.4 |
U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | General insurance account [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | General insurance account [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
U.S. Pension Plans [Member] | General insurance account [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 57.2 | 67.2 |
Actual return on plan assets | 1.5 | 4 |
Defined Benefit Plan, Divestitures, Plan Assets | 0 | (9.9) |
Foreign currency exchange rates | (4.1) | (4.6) |
Fair value of plan assets at the end of the year | 54.2 | 57.2 |
Non-U.S. Pension Plans [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 46.7 | |
Fair value of plan assets at the end of the year | 44.9 | 46.7 |
Non-U.S. Pension Plans [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 5 | |
Fair value of plan assets at the end of the year | 4 | 5 |
Non-U.S. Pension Plans [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 5.5 | |
Fair value of plan assets at the end of the year | 5.3 | 5.5 |
Non-U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Cash and cash equivalents [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Corporate debt securities [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | U.S. government debt securities [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | State and municipal debt securities [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Corporate common stock [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 46.7 | |
Fair value of plan assets at the end of the year | 44.9 | 46.7 |
Non-U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Registered investment company funds [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 5 | |
Fair value of plan assets at the end of the year | 4 | 5 |
Non-U.S. Pension Plans [Member] | Common trust funds [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | General insurance account [Member] | (Level 1) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | General insurance account [Member] | (Level 2) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 0 | |
Fair value of plan assets at the end of the year | 0 | 0 |
Non-U.S. Pension Plans [Member] | General insurance account [Member] | (Level 3) | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets at the beginning of the year | 5.5 | |
Fair value of plan assets at the end of the year | $ 5.3 | $ 5.5 |