Stock-Based Compensation Plans (Information Regarding Stock Options) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants outstanding	0	0	0
Options granted during period	114,943
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 2,000,000
Shares
Outstanding — beginning of year	0	84,261	97,962
Granted	114,943	0	0
Exercised	0	(84,261)	(13,701)
Canceled	0	0	0
Outstanding — end of year	114,943	0	84,261	97,962
Exercisable — end of year	0	0	84,261
Weighted Average Exercise Price
Outstanding — beginning of year	$ 0.00	$ 17.42	$ 16.61
Exercised	0.00	17.42	11.66
Canceled	0.00	0.00	0.00
Outstanding — end of year	48.63	0.00	17.42	$ 16.61
Exercisable — end of year	$ 0.00	$ 0.00	$ 17.42
Weighted Average Remaining Contractual Life			9 years 3 months	1 year
Total intrinsic value of stock options exercised		$ 2,400,000	$ 1,000,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted during period	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 0	$ 0
Recognition of unearned compensation, (years)	2 years
General expiration period, from date of grant or time of termination (years)		10 years
Weighted Average Exercise Price
Number of stock options vested	$ 0	$ 0	$ 0
Stock Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period (years)		3 years