Convertible Debentures and Credit Arrangements - Convertible Senior Debentures due 2018 - Additional Information (Detail) (USD $)	1 Months Ended	6 Months Ended
	Nov. 30, 2012	Jun. 30, 2013
Convertible Senior Debentures due 2018
Debt Instrument [Line Items]
Conversion rate of common stock		55.17
Principal amount of convertible debentures		$ 1,000
Conversion price (in dollars per share)		$ 18.13
Closing price for common stock		$ 16.05
Cash redemption description		On or after November 15, 2016, the Company may redeem for cash any of the 2018 Debentures if the last reported sale price of the Company’s common stock exceeds 140% of the conversion price for at least 20 trading days during the period of 30 consecutive trading days ending on the trading day before the date that notice of redemption is given, including the last trading day of such period. Upon any redemption of the 2018 Debentures, the Company will pay a redemption price of 100% of their principal amount, plus accrued and unpaid interest to, but excluding, the date of redemption, and additional interest, if any.
Debentures redemption price		100.00%
Sales price of common stock to conversion price		140.00%
Change in control due to debentures redemption		50.00%
Percentage of principal amount and accrued and unpaid interest for repurchase of debt		100.00%
Outstanding debentures		55,000,000
Fair value of Debentures outstanding		60,500,000
Gross carrying amount of equity component		6,400,000
Principal amount of liability component		55,000,000
Unamortized discount		6,000,000
Carrying value of liability component		49,000,000
Additional interest expenses		500,000
Interest rate on debentures	5.25%	8.70%
Convertible senior debentures, convertible latest date		Nov. 15, 2017
Number of days within 30 consecutive trading days in which the closing price of the entity's common stock exceeded the conversion price giving the holders of the debentures an option (in days)		20 days
Number of consecutive trading days during which the closing price of the entity's common stock exceeded the conversion price for at least 20 days giving the holders of the debentures an option (in days)		30 days
Number of days after five consecutive trading days in which the trading price per $1,000 principal amount was less than 98% of the product of the closing sale price per share of Company common stock multiplied by the conversion rate on each such trading day (in days)		5 days
Number of consecutive trading days during which the trading price per $1,000 principal amount for at least five days was less than 98% of the product of the closing sale price per share of Company common stock multiplied by the conversion rate on each such trading day (in days)		5 days
Closing price is percentage of conversion price		98.00%
Aggregate face value of convertible senior debentures	55,000,000
Convertible senior debentures, expiration year	2018
Convertible senior debentures, interest payment description		Interest on the 2018 Debentures is payable semi-annually on May 15 and November 15.
Convertible Senior Debentures due 2018 | Minimum
Debt Instrument [Line Items]
Percentage of the closing sales price of the entity's common stock that the conversion price exceeded giving the holders of the debentures an option (as a percent)		130.00%
Convertible Senior Debentures due 2014
Debt Instrument [Line Items]
Interest rate on debentures	10.125%
Aggregate face value of convertible senior debentures		$ 46,900,000
Convertible senior debentures, expiration year	2014