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Financial Statement Revisions - Statements of Changes in Equity (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Jun. 30, 2017 | Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances |  |  | $ 3,716.0 | $ 3,716.0 |  |  |  |
Net income | $ 551.5 | $ 87.7 |  | 581.1 | $ 465.3 |  |  |
Change in foreign currency translation, net of tax | 0.0 | 0.2 |  | 0.2 | (0.4) |  |  |
Ending Balances | 3,337.2 |  |  | 3,337.2 |  | $ 3,716.0 |  |
As previously reported |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 3,764.1 |  | 3,737.2 | 3,737.2 | 4,368.0 | 4,368.0 |  |
Net income |  | 88.6 | 36.4 |  | 470.4 | 419.8 | $ 279.5 | $ 290.0
Ending Balances |  |  | 3,764.1 |  |  | 3,737.2 | 4,368.0 |
Adjustments |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | (29.2) |  | (21.2) | (21.2) | (10.4) | (10.4) |  |
Net income |  | (0.9) | (6.7) |  | (5.1) | (10.8) | (2.8) | (7.1)
Ending Balances |  |  | (29.2) |  |  | (21.2) | (10.4) |
As revised |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 3,734.9 |  | 3,716.0 | 3,716.0 | 4,357.6 | 4,357.6 |  |
Net income |  | 87.7 | 29.7 |  | 465.3 | 409.0 | 276.7 | 282.9
Ending Balances |  |  | 3,734.9 |  |  | 3,716.0 | 4,357.6 |
Common shares and paid-in surplus |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances |  |  | 810.7 | 810.7 | 978.2 | 978.2 |  |
Repurchases and retirements of common shares |  |  |  | (147.9) | (188.1) |  |  |
Net income |  |  |  | 0.0 | 0.0 |  |  |
Dividends declared on common shares |  |  |  | 0.0 | 0.0 |  |  |
Ending Balances | 669.3 | 809.8 |  | 669.3 | 809.8 | 810.7 | 978.2 |
Common shares and paid-in surplus | As previously reported |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 815.1 |  | 810.7 | 810.7 | 978.2 | 978.2 | 1,034.7 |
Ending Balances |  | 809.8 | 815.1 |  | 809.8 | 810.7 | 978.2 | 1,034.7
Common shares and paid-in surplus | Adjustments |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 0.7 |  | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
Ending Balances |  | 0.0 | 0.7 |  | 0.0 | 0.0 | 0.0 | 0.0
Common shares and paid-in surplus | As revised |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 815.8 |  | 810.7 | 810.7 | 978.2 | 978.2 | 1,034.7 |
Ending Balances |  | 809.8 | 815.8 |  | 809.8 | 810.7 | 978.2 | 1,034.7
Retained earnings |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances |  |  | 2,776.6 | 2,776.6 | 3,075.0 | 3,075.0 |  |
Repurchases and retirements of common shares |  |  |  | (575.9) | (678.6) |  |  |
Net income |  |  |  | 604.7 | 440.7 |  |  |
Dividends declared on common shares |  |  |  | (4.6) | (5.4) |  |  |
Ending Balances | 2,800.8 | 2,831.7 |  | 2,800.8 | 2,831.7 | 2,776.6 | 3,075.0 |
Retained earnings | As previously reported |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 2,835.2 |  | 2,797.2 | 2,797.2 | 3,084.9 | 3,084.9 | 3,010.5 | 2,801.9
Repurchases and retirements of common shares |  |  | (7.2) |  | (678.6) | (694.8) | (217.2) | (97.4)
Net income |  |  | 49.8 |  | 445.8 | 412.5 | 297.6 | 312.2
Dividends declared on common shares |  |  | (4.6) |  | (5.4) | (5.4) | (6.0) | (6.2)
Net other changes in AOCI |  |  | 0.0 |  | 113.6 | 113.9 | (34.6) | 66.6
Ending Balances |  | 2,846.7 | 2,835.2 |  | 2,846.7 | 2,797.2 | 3,084.9 | 3,010.5
Retained earnings | Adjustments |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | (27.7) |  | (20.6) | (20.6) | (9.9) | (9.9) | (7.5) | (0.5)
Repurchases and retirements of common shares |  |  | 0.0 |  | 0.0 | 0.0 | 0.0 | 0.0
Net income |  |  | (7.1) |  | (5.1) | (10.7) | (2.4) | (7.0)
Dividends declared on common shares |  |  | 0.0 |  | 0.0 | 0.0 | 0.0 | 0.0
Net other changes in AOCI |  |  | 0.0 |  | 0.0 | 0.0 | 0.0 | 0.0
Ending Balances |  | (15.0) | (27.7) |  | (15.0) | (20.6) | (9.9) | (7.5)
Retained earnings | As revised |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 2,807.5 |  | 2,776.6 | 2,776.6 | 3,075.0 | 3,075.0 | 3,003.0 | 2,801.4
Repurchases and retirements of common shares |  |  | (7.2) |  | (678.6) | (694.8) | (217.2) | (97.4)
Net income |  |  | 42.7 |  | 440.7 | 401.8 | 295.2 | 305.2
Dividends declared on common shares |  |  | (4.6) |  | (5.4) | (5.4) | (6.0) | (6.2)
Net other changes in AOCI |  |  | 0.0 |  | 113.6 | 113.9 | (34.6) | 66.6
Ending Balances |  | 2,831.7 | 2,807.5 |  | 2,831.7 | 2,776.6 | 3,075.0 | 3,003.0
AOCI, after tax |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances |  |  | (4.6) | (4.6) | (149.9) | (149.9) |  |
Repurchases and retirements of common shares |  |  |  | 0.0 | 0.0 |  |  |
Net income |  |  |  | 0.0 | 0.0 |  |  |
Dividends declared on common shares |  |  |  | 0.0 | 0.0 |  |  |
Ending Balances | (1.3) | (4.5) |  | (1.3) | (4.5) | (4.6) | (149.9) |
AOCI, after tax | As previously reported |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | (3.0) |  | (4.6) | (4.6) | (149.9) | (149.9) | (49.5) | 52.1
Ending Balances |  | (4.3) | (3.0) |  | (4.3) | (4.6) | (149.9) | (49.5)
AOCI, after tax | Adjustments |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | (1.3) |  | 0.0 | 0.0 | 0.0 | 0.0 | 7.4 | 0.5
Ending Balances |  | (0.2) | (1.3) |  | (0.2) | 0.0 | 0.0 | 7.4
AOCI, after tax | As revised |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | (4.3) |  | (4.6) | (4.6) | (149.9) | (149.9) | (42.1) | 52.6
Ending Balances |  | (4.5) | (4.3) |  | (4.5) | (4.6) | (149.9) | (42.1)
Total |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances |  |  | 3,582.7 | 3,582.7 | 3,903.3 | 3,903.3 |  |
Repurchases and retirements of common shares |  |  |  | (723.8) | (866.7) |  |  |
Net income |  |  |  | 604.7 | 440.7 |  |  |
Dividends declared on common shares |  |  |  | (4.6) | (5.4) |  |  |
Ending Balances | 3,468.8 | 3,637.0 |  | 3,468.8 | 3,637.0 | 3,582.7 | 3,903.3 |
Total | As previously reported |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 3,647.3 |  | 3,603.3 | 3,603.3 | 3,913.2 | 3,913.2 | 3,995.7 |
Ending Balances |  | 3,652.2 | 3,647.3 |  | 3,652.2 | 3,603.3 | 3,913.2 | 3,995.7
Total | Adjustments |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | (28.3) |  | (20.6) | (20.6) | (9.9) | (9.9) | (0.1) |
Ending Balances |  | (15.2) | (28.3) |  | (15.2) | (20.6) | (9.9) | (0.1)
Total | As revised |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 3,619.0 |  | 3,582.7 | 3,582.7 | 3,903.3 | 3,903.3 | 3,995.6 |
Ending Balances |  | 3,637.0 | 3,619.0 |  | 3,637.0 | 3,582.7 | 3,903.3 | 3,995.6
Non-controlling interest |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances |  |  | 133.3 | 133.3 | 454.3 | 454.3 |  |
Repurchases and retirements of common shares |  |  |  | (5.2) | 0.0 |  |  |
Net income |  |  |  | (23.6) | 24.6 |  |  |
Dividends declared on common shares |  |  |  | 0.0 | 0.0 |  |  |
Ending Balances | (131.6) | 148.7 |  | (131.6) | 148.7 | 133.3 | 454.3 |
Non-controlling interest | As previously reported |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 116.8 |  | 133.9 | 133.9 | 454.8 | 454.8 | 542.7 | 491.7
Net income |  |  | (13.4) |  | 24.6 | 7.3 | (18.1) | (22.2)
Other changes in NCI |  |  | (3.7) |  | (330.2) | (328.2) | (69.8) | 73.2
Ending Balances |  | 149.2 | 116.8 |  | 149.2 | 133.9 | 454.8 | 542.7
Non-controlling interest | Adjustments |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | (0.9) |  | (0.6) | (0.6) | (0.5) | (0.5) | (0.1) | 0.0
Net income |  |  | 0.4 |  | 0.0 | (0.1) | (0.4) | (0.1)
Other changes in NCI |  |  | (0.7) |  | 0.0 | 0.0 | 0.0 | 0.0
Ending Balances |  | (0.5) | (0.9) |  | (0.5) | (0.6) | (0.5) | (0.1)
Non-controlling interest | As revised |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 115.9 |  | 133.3 | 133.3 | 454.3 | 454.3 | 542.6 | 491.7
Net income |  |  | (13.0) |  | 24.6 | 7.2 | (18.5) | (22.3)
Other changes in NCI |  |  | (4.4) |  | (330.2) | (328.2) | (69.8) | 73.2
Ending Balances |  | 148.7 | 115.9 |  | 148.7 | 133.3 | 454.3 | 542.6
Total Equity |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances |  |  | 3,716.0 | 3,716.0 | 4,357.6 | 4,357.6 |  |
Repurchases and retirements of common shares |  |  |  | (729.0) | (866.7) |  |  |
Net income |  |  |  | 581.1 | 465.3 |  |  |
Dividends declared on common shares |  |  |  | (4.6) | (5.4) |  |  |
Ending Balances | 3,337.2 | 3,785.7 |  | 3,337.2 | 3,785.7 | 3,716.0 | 4,357.6 |
Total Equity | As previously reported |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | 3,764.1 |  | 3,737.2 | 3,737.2 | 4,368.0 | 4,368.0 | 4,538.4 |
Ending Balances |  | 3,801.4 | 3,764.1 |  | 3,801.4 | 3,737.2 | 4,368.0 | 4,538.4
Total Equity | Adjustments |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | (29.2) |  | (21.2) | (21.2) | (10.4) | (10.4) | (0.2) |
Ending Balances |  | (15.7) | (29.2) |  | (15.7) | (21.2) | (10.4) | (0.2)
Total Equity | As revised |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Beginning Balances | $ 3,734.9 |  | 3,716.0 | 3,716.0 | 4,357.6 | 4,357.6 | 4,538.2 |
Ending Balances |  | $ 3,785.7 | 3,734.9 |  | 3,785.7 | 3,716.0 | 4,357.6 | 4,538.2
Foreign Currency Gain (Loss) | Common shares and paid-in surplus |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Change in foreign currency translation, net of tax |  |  |  | 0.0 | 0.0 |  |  |
Foreign Currency Gain (Loss) | Retained earnings |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Change in foreign currency translation, net of tax |  |  |  | 0.0 | 0.0 |  |  |
Foreign Currency Gain (Loss) | AOCI, after tax |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Change in foreign currency translation, net of tax |  |  |  | 0.4 | 32.1 |  |  |
Foreign Currency Gain (Loss) | AOCI, after tax | As previously reported |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Change in foreign currency translation, net of tax |  |  | 1.6 |  | 32.0 | 31.4 | (65.8) | (168.2)
Foreign Currency Gain (Loss) | AOCI, after tax | Adjustments |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Change in foreign currency translation, net of tax |  |  | (1.3) |  | (0.2) | 0.0 | (7.4) | 6.9
Foreign Currency Gain (Loss) | AOCI, after tax | As revised |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Change in foreign currency translation, net of tax |  |  | $ 0.3 |  | 31.8 | $ 31.4 | $ (73.2) | $ (161.3)
Foreign Currency Gain (Loss) | Total |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Change in foreign currency translation, net of tax |  |  |  | 0.4 | 32.1 |  |  |
Foreign Currency Gain (Loss) | Non-controlling interest |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Change in foreign currency translation, net of tax |  |  |  | 0.1 | 0.1 |  |  |
Foreign Currency Gain (Loss) | Total Equity |  |  |  |  |  |  |  |
Increase (Decrease) in Shareholders' Equity |  |  |  |  |  |  |  |
Change in foreign currency translation, net of tax |  |  |  | $ 0.5 | $ 32.2 |  |  |

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- Definition Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4I -URI http://asc.fasb.org/extlink&oid=65897068&loc=SL4590271-111686 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=68079674&loc=SL4568740-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=68079674&loc=SL4568447-111683 + Details
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