Financing Arrangements - Additional Information (Detail) $ / shares in Units, shares in Millions			3 Months Ended	9 Months Ended
	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($) $ / shares shares	Mar. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($) $ / shares shares	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Debt instrument interest rate				1.25%		1.25%
Number of common shares converted upon debt conversion for each $1000 principal amount		12.5170
Principal amount of notes per conversion		$ 1,000			$ 1,000
Conversion price of convertible notes | $ / shares		$ 79.89			$ 79.89
Earliest conversion date		Jul. 01, 2019
Number of least trading days required within consecutive trading days		5 days
Number of consecutive business days following consecutive trading days		5 days
Concentration risk percentage		98.00%
Debt issuance costs		$ 7,300,000
Liability issuance costs		6,200,000			$ 6,200,000
Equity issuance costs		$ 1,100,000			1,100,000
Aggregate amount for convertible hedge				$ 0	42,125,000
Aggregate proceeds from the sale of warrants				0	$ 23,625,000
Deferred tax liability				$ 53,842,000		$ 26,855,000
Revolving Credit facility	$ 500,000,000		$ 500,000,000
Period of revolving credit facility	5 years
Credit agreement expiration date	Mar. 31, 2020
Option to increase revolving credit facility	$ 100,000,000
Maximum principle amount	$ 600,000,000		$ 600,000,000
Percentage of other equity interests in domestic subsidiaries	100.00%
Percentage of other equity interests in foreign subsidiaries	65.00%
Minimum consolidated interest coverage ratio	3.50		3.50
Actual consolidated leverage ratio				2.49
Actual interest coverage ratio				18.30
Carrying Amount				$ 419,426,000		$ 356,602,000
Percentage of weighted average interest rate of borrowings				2.30%		2.30%
Outstanding letters of credit				$ 5,200,000		$ 5,100,000
Scenario One, Leverage Ratio
Debt Instrument [Line Items]
Maximum consolidated leverage ratio			3.25
Scenario Two, Leverage Ratio
Debt Instrument [Line Items]
Maximum consolidated leverage ratio			3.50
Revolving Credit Facility
Debt Instrument [Line Items]
Convertible debt maturity term	90 days
Note Hedge
Debt Instrument [Line Items]
Common stock purchased | shares		3.1			3.1
Aggregate amount for convertible hedge		$ 42,100,000
Deferred tax asset		$ 16,500,000			$ 16,500,000
Warrants related to the issuance of convertible senior notes
Debt Instrument [Line Items]
Common stock purchased | shares		3.1			3.1
Common stock price per share | $ / shares		$ 97.12			$ 97.12
Aggregate proceeds from the sale of warrants		$ 23,600,000
Minimum
Debt Instrument [Line Items]
Conversion price of convertible notes | $ / shares		$ 79.89			79.89
Number of least trading days required within consecutive trading days		20 days
Number of consecutive trading days		30 days
Percentage of applicable conversion price		130.00%
Minimum | LIBOR
Debt Instrument [Line Items]
Interest rate on borrowings	0.25%
Minimum | Base Rate
Debt Instrument [Line Items]
Interest rate on borrowings	1.25%
Maximum
Debt Instrument [Line Items]
Conversion price of convertible notes | $ / shares		$ 97.12			$ 97.12
Maximum | LIBOR
Debt Instrument [Line Items]
Interest rate on borrowings	0.75%
Maximum | Base Rate
Debt Instrument [Line Items]
Interest rate on borrowings	1.75%
Convertible Debt
Debt Instrument [Line Items]
Aggregate principal amount		$ 250,000,000		$ 250,000,000	$ 250,000,000	250,000,000
Debt instrument interest rate		1.25%			1.25%
Debt instrument maturity date		Oct. 01, 2019
Principal amount of notes per conversion		$ 1,000			$ 1,000
Optional right of debt instrument holders to convert debt instrument into cash, portion of principal amount		100.00%
Effective interest rate of debt		4.751%			4.751%
Remaining life of notes				4 years
Deferred tax liability		$ 15,400,000			$ 15,400,000
Carrying Amount				$ 218,176,000		212,852,000
Revolving Credit Facility
Debt Instrument [Line Items]
Carrying Amount				201,250,000
Unused borrowing capacity under Credit Agreement				293,500,000
Senior secured credit facility
Debt Instrument [Line Items]
Carrying Amount				$ 201,250,000		$ 143,750,000