Consolidated Balance Sheets (Parenthetical) $ in Thousands, shares in Millions	Jun. 30, 2017 USD ($) shares	Jun. 30, 2017 £ / shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2016 £ / shares
Allowances for doubtful accounts	$ 17,480		$ 15,253
Reserves for inventories	76,463		72,596
Accumulated depreciation of property, plant and equipment	356,213		319,473
Accumulated amortization of intangible assets	$ 1,405,217		$ 1,254,360
Common stock, nominal value | £ / shares		£ 0.01		£ 0.01
Common stock, shares issued | shares	186.7		190.1
Common stock, shares outstanding | shares	186.7		190.1