Stock-Based Compensation And Other Employee Benefit Plans (Summary of Stock Options) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012		Dec. 31, 2011
Stock Options Outstanding [Roll Forward]
Options outstanding, vested, beginning balance	1,053,825		1,445,774		1,445,774
Options exercised	(194,200)		(20,000)
Options canceled/forfeited	0		0
Options outstanding, vested, ending balance	859,625		1,425,774		1,053,825		1,445,774
Weighted Average Exercise Price [Roll Forward]
Weighted average exercise price, vested, beginning balance	$ 10.55		$ 10.25		$ 10.25
Weighted average exercise price, exercised	$ 10.02		$ 5.37
Weighted average exercise price, canceled/forfeited	$ 0.00		$ 0.00
Weighted average exercise price, vested, ending balance	$ 10.66		$ 10.32		$ 10.55		$ 10.25
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options exercisable	859,625		1,425,774
Options exercisable, weighted average exercise price	$ 10.66		$ 10.32
Options outstanding, vested, weighted average remaining contractual life	2 years 0 months 22 days		2 years 11 months 19 days		2 years 3 months 22 days		3 years 1 month 28 days
Options exercisable, weighted average remaining contractual life	2 years 0 months 22 days		2 years 11 months 19 days
Options outstanding, aggregate intrinsic value, vested	$ 15.9	[1]	$ 11.1	[1]	$ 15.2	[1]	$ 10.3	[1]
Options exercisable, aggregate intrinsic value, vested	$ 15.9	[1]	$ 11.1	[1]

[1] Amount represents the difference between the exercise price and the market price of the Company’s stock on the last trading day of the corresponding period, multiplied by the number of in-the-money options.