Cash Dividends (Summary of Conversion Rates for Convertible Notes) (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013
Series 2012 Notes [Member]
Debt Instrument [Line Items]
Conversion Rate per $1,000 Principal Amount (in Ratio)	$ 173.200
Approximate Conversion Price Per Common Share (in Dollars per Share)	$ 5.77
Effective Date (Date)	Mar. 01, 2013
May 2015 Notes [Member]
Debt Instrument [Line Items]
Conversion Rate per $1,000 Principal Amount (in Ratio)	$ 151.6248
Approximate Conversion Price Per Common Share (in Dollars per Share)	$ 6.60
Effective Date (Date)	Mar. 01, 2013
February 2015 Notes [Member]
Debt Instrument [Line Items]
Conversion Rate per $1,000 Principal Amount (in Ratio)	$ 173.200
Approximate Conversion Price Per Common Share (in Dollars per Share)	$ 5.77
Effective Date (Date)	Mar. 06, 2013