Debt - 2015 Senior Unsecured Notes - Additional Information (Detail) - EUR (€) € in Millions		12 Months Ended
	Aug. 19, 2015	Dec. 31, 2015
Debt Instrument [Line Items]
Senior unsecured notes, payable term		Interest on the notes will be payable on March 1 and September 1 of each year
Senior unsecured notes, redemption description		We may redeem some or all of the notes at any time prior to March 1, 2019 at a “make whole” redemption price. On or after March 1, 2019, we may redeem some or all of the notes at a premium that will decrease over time. In addition, at any time prior to March 1, 2019, we may redeem up to 35% of the notes at a redemption price equal to 106.375% of the aggregate principal amount thereof, plus accrued and unpaid interest thereon, using proceeds from one or more equity offerings. In the event of a change in control, each holder of the notes may require us to repurchase some or all of the notes at a repurchase price equal to 101% of the aggregate principal amount of the notes plus accrued and upaid interest to the date of purchase.
2015 Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Senior unsecured notes face amount	€ 500
Senior unsecured notes, payable term		Interest on the notes will be payable annually on August 19 of each year
Senior unsecured notes commencing date of payment	Aug. 19, 2016
Senior unsecured notes, interest rate	4.00%	4.00%
Senior unsecured notes, maturity date	Aug. 19, 2022
Senior unsecured notes, redemption period	90 days
Senior unsecured notes, redemption price percentage	101.00%
Senior unsecured notes, redemption description		Notes are redeemed prior to 90 days before maturity, the redemption price will be 100% of their principal amount, plus a make-whole premium, plus accrued and unpaid interest to, but excluding, the applicable redemption date. Within the period beginning on or after 90 days before maturity, the Notes may be redeemed, in whole or in part, at a redemption price equal to 100% of their principal amount, plus accrued and unpaid interest to, but excluding, the applicable redemption date. The 2015 Senior Unsecured Notes are fully and unconditionally guaranteed on an unsecured basis by the Company. In the event of a change of control, each holder of the Notes may require us to repurchase some or all of our Notes at a repurchase price equal to 101% of the aggregate principal amount of the Notes plus accrued and unpaid interest to the date of the purchase.
2015 Senior Unsecured Notes [Member] | Redeemed Prior to 90 Days [Member]
Debt Instrument [Line Items]
Senior unsecured notes, redemption price percentage	100.00%
2015 Senior Unsecured Notes [Member] | Redeemed Beginning on or After 90 Days [Member]
Debt Instrument [Line Items]
Senior unsecured notes, redemption price percentage	100.00%