Debt - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended			9 Months Ended			0 Months Ended		0 Months Ended		9 Months Ended					0 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 17, 2014 Revolving Credit Facility extension	Sep. 17, 2014 Revolving Credit Facility	Sep. 16, 2014 Revolving Credit Facility	Sep. 30, 2014 Revolving Credit Facility Minimum	Sep. 30, 2014 Revolving Credit Facility Maximum	Sep. 30, 2014 Revolving Credit Facility, Additional Borrowing Capacity	Sep. 16, 2014 3.875% Senior Notes [Member] Senior Notes [Member]	Sep. 16, 2014 3.875% Senior Notes [Member] Senior Notes [Member]	Sep. 16, 2014 4.375% Senior Notes [Member] Senior Notes [Member]	Sep. 16, 2014 4.375% Senior Notes [Member] Senior Notes [Member]	Sep. 30, 2014 Senior Notes [Member]	Sep. 30, 2014 2021 and 2024 Notes [Member] Senior Notes [Member]	Sep. 30, 2014 Letter of Credit	Sep. 30, 2014 European Lease Agreement Replaced Line of Credit	Dec. 31, 2013 European Lease Agreement Replaced Line of Credit	Oct. 16, 2014 Subsequent Event [Member] 6.35% Senior Notes [Member] Senior Notes [Member]	Oct. 16, 2014 Subsequent Event [Member] 6.35% Senior Notes [Member] Senior Notes [Member]	Sep. 30, 2014 Treasury Rate [Member] 2021 and 2024 Notes [Member] Senior Notes [Member] Minimum	Sep. 30, 2014 Treasury Rate [Member] 2021 and 2024 Notes [Member] Senior Notes [Member] Maximum
Debt Instrument [Line Items]
Par value of debt												$ 275,000,000		$ 275,000,000
Interest rate of debt												3.875%		4.375%							6.35%
Debt Instrument, Maturity Date											Sep. 30, 2021		Dec. 15, 2024
Debt issued, percent of par											99.50%		99.60%
Effective yield percentage												3.951%		4.422%
Debt redemption price, percentage																100.00%
Debt redemption price discount rate, basis spread on Treasury Rate																						0.25%	0.30%
Deferred finance costs																4,200,000
Debt retired																					200,000,000
Redemption premium																				17,400,000
Loss on early retirement of debt	14,890,000	0	14,890,000	0																14,900,000
Senior Notes redemption price description															We may redeem the Senior Notes, in whole or in part, at a redemption price of the greater of 100% of the principal amount of the Senior Notes or the present value of remaining scheduled payments of principal and interest discounted at the applicable Treasury Rate plus 0.25%.
Expiration date					Sep. 17, 2019
Maximum borrowing capacity						450,000,000	350,000,000			200,000,000
Number of extension					2
Term of each extension (in years)					1 year
Commitment fee charged on unused portion of facility								0.125%	0.25%
Borrowings outstanding	0		0														5,000,000	1,300,000	1,500,000
Amount available for borrowing	$ 445,000,000		$ 445,000,000