Condensed Consolidated Balance Sheets (Parenthetical) |
Sep. 30, 2016
£ / shares
shares
|
Sep. 30, 2016
$ / shares
shares
|
Dec. 31, 2015
£ / shares
shares
|
Dec. 31, 2015
$ / shares
shares
|
---|---|---|---|---|
Treasury shares, shares held (in shares) | 7,200,000 | 7,200,000 | 7,600,000 | 7,600,000 |
Class A ordinary shares, U.S. [Member] | ||||
Common stock, par value per share (in dollars per share or pounds sterling per share) | $ / shares | $ 0.10 | $ 0.1 | ||
Common shares, shares authorized (in shares) | 450,000,000.0 | 450,000,000.0 | 450,000,000 | 450,000,000 |
Common shares, shares issued (in shares) | 308,500,000 | 308,500,000 | 242,900,000 | 242,900,000 |
Common Class B, Par Value In GBP [Member] | ||||
Common stock, par value per share (in dollars per share or pounds sterling per share) | £ / shares | £ 1 | £ 1 | ||
Common shares, shares authorized (in shares) | 50,000 | 50,000 | 50,000 | 50,000 |
Common shares, shares issued (in shares) | 50,000 | 50,000 | 50,000 | 50,000 |