Employee Benefit Plans (Cash-Equivalent Stock Awards) (Details) (USD $)	12 Months Ended	3 Months Ended
	Dec. 31, 2013 Cash Equivalent Stock Awards [Member]	Mar. 31, 2014 Cash Equivalent Stock Awards Rsus [Member]	Mar. 31, 2014 Cash Equivalent Stock Awards Performance Based [Member]
Activity:
Outstanding, beginning of year, shares		683,028	343,987
Granted, shares		146,054	83,146
Additional awards granted due to achievement of performance criteria, shares		0	34,965
Forfeited, shares		(960)	0
Fully vested, shares		(250,640)	(151,480)
Outstanding, end of year, shares		577,482	310,618
Weighted average grant date fair value:
Outstanding, beginning of year - weighted average grant date fair value		$ 74.10	$ 71.02
Granted - weighted average grant date fair value		$ 100.67	$ 100.67
Additional awards granted due to achievement of performance criteria - weighted average grant date fair value		$ 0.00	$ 61.51
Forfeited - weighted average grant date fair value		$ (77.72)	$ 0
Vested - weighted average grant date fair value		$ (64.41)	$ (61.51)
Outstanding, end of year - weighted average grant date fair value		$ 83.81	$ 82.52
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Vesting period	4 years