Stock-Based Compensation, Dividend Restrictions, And Calculations Of Earnings Per Share Of Common Stock (Narrative) (Detail) (USD $)	1 Months Ended				12 Months Ended						12 Months Ended					1 Months Ended
	Sep. 30, 2012	Apr. 30, 2012	Feb. 23, 2012	Jan. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 27, 2013	Feb. 27, 2013 Subsequent Event [Member]	Dec. 31, 2012 2012 LTIP [Member]	Dec. 31, 2012 Time-Based Restricted Stock [Member]	Dec. 31, 2011 Time-Based Restricted Stock [Member]	Dec. 31, 2010 Time-Based Restricted Stock [Member]	Dec. 31, 2012 Time Based Restricted Stock Awards [Member]	Dec. 31, 2012 Performance Based Restricted Stock Award [Member]	Sep. 30, 2012 Non Employee Directors [Member]	May 31, 2012 Non Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock authorized for issuance					10,000,000					8,000,000
Stock-based compensation expense					$ 0	$ 0	$ 0				$ 11,000,000	$ 6,000,000	$ 5,000,000
Eligible percentage of common stock over the performance period target award minimum					25.00%
Eligible percentage of common stock over the performance period target award maximum					200.00%
Requisite service period (years)					3 years
Restricted stock awards	150,330	150,330		150,330
Unrestricted stock awards	5,305	5,305		5,305
Vesting Period														3 years	1 year	1 year	1 year
Restricted stock units were granted to each non-employee director	40,749
Targeted performance criteria					100.00%
Unrecognized compensation expense					13,000,000
Costs recognized, weighted average period (years)					2 years
Stock options outstanding					0	30,925
Stock option expiration (years)					10 years
Options expired, weighted-average exercise price					$ 0.00	$ 20.75
Weighted-average remaining contractual term						11 days
Number of shares of common stock non-employee directors are entitled					1,000
Deferred compensation balance					1,000,000	1,000,000
Ratio of equity to total capitalization					30.00%
Retained earnings					1,109,000,000	1,072,000,000
Public offering price					$ 19.25			$ 17.39
Underwriting discount					$ 0.67375
Common stock issued									17,922,077
Proceeds used to repay the term loan									312,000,000
Dilutive effect of earnings per share					$ 0.01
Purchases of common stock minimum per calendar month					25
Purchases of common stock maximum per calendar year					$ 200,000
Shares issued and sold under the DRP					2,000,000	2,000,000	2,000,000
Excluded shares for potential issuance of equity forward transaction			31,000,000