Compensation and Benefit Plans (Restricted Stock Units) (Details) (Restricted Stock Units, USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Restricted Stock Units
Restricted Stock Units
Nonvested, at the beginning of the period (in shares)	111,220
Granted (in shares)	0
Forfeited (in shares)	(1,065)
Paid out (in shares)	(37,221)
Affiliate transfers - net (in shares)	(901)
Nonvested, at the end of the period (in shares)	72,033	111,220
Weighted-Average Grant-Date Fair Value
Nonvested, at the beginning of the period (in dollars per share)	$ 38.36
Granted (in dollars per share)	$ 0.00	$ 43.16	$ 38.03
Forfeited (in dollars per share)	$ 40.69
Paid out (in dollars per share)	$ 33.89
Affiliate transfers - net (in dollars per share)	$ 40.46
Nonvested, at the end of the period (in dollars per share)	$ 40.61	$ 38.36
Unrecognized compensation cost	$ 0.6
Vesting period	3 years 2 days