Long-Term Debt Senior Notes (Detail) (USD $)	3 Months Ended		12 Months Ended										0 Months Ended	3 Months Ended
	Mar. 31, 2013	Jun. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Sep. 09, 2013 5½% Senior Notes [Member] Senior Notes [Member]	Sep. 09, 2013 5½% Senior Notes [Member] Prior to August 1, 2016 Senior Notes [Member]	Sep. 09, 2013 5½% Senior Notes [Member] Prior to August 1, 2017 Senior Notes [Member]	Mar. 23, 2012 5% Senior Notes due 2020 [Member] Senior Notes [Member]	Mar. 23, 2012 5% Senior Notes due 2020 [Member] Prior to April 01, 2016 Senior Notes [Member]	Mar. 23, 2012 5% Senior Notes due 2020 [Member] Prior to April 1, 2015 Senior Notes [Member]	Mar. 23, 2012 5% Senior Notes due 2020 [Member] Prior to April 1, 2016 Senior Notes [Member]	Apr. 09, 2012 7.25 % Senior Notes [Member] Senior Notes [Member]	Jun. 30, 2012 7.25 % Senior Notes [Member] Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount						$ 300,000,000			$ 500,000,000
Debt Instrument Offering Price Percentage						100.00%			100.00%
Debt Instrument Redemption Date							August 1, 2016	August 1, 2017		April 1, 2016	April 1, 2015	April 1, 2016
Maximum Redemption Percent Allowed And Limited To Proceeds From Equity Offering							35.00%				35.00%
Debt Redemption Price Percent Of Principal Amount							105.50%	100.00%			105.00%	100.00%	112.3715%
Redemption Price Percent If Change In Control Occurs						101.00%			101.00%
Extinguishment of Debt, Amount													250,000,000
Early Repayment of Subordinated Debt													280,900,000
Loss on early extinguishment of debt	$ (2,100,000)	$ (38,700,000)	$ (2,068,000)	$ (38,704,000)	$ (976,000)									$ (38,700,000)