Employee compensation Restricted Stock Option Awards (Details 2) (Employee Stock Option, USD $) In Millions, except Share data in Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014		Dec. 31, 2013
Employee Stock Option
Restricted stock option awards
Outstanding at the beginning of the period (in shares)	1,229
Granted (in shares)	336
Exercised (in shares)	(95)	[1]
Expired or canceled (in shares)	0
Forfeited (in shares)	(47)
Outstanding at the end of the period (in shares)	1,423		1,229
Vested and exercisable at end of period (in shares)	352	[2]
Vested, exercisable, and expected to vest at end of period (in shares)	1,390	[3]
Weighted-average exercise price (per option)
Outstanding at the beginning of the period (in dollars per share)	$ 19.32
Granted (in dollars per share)	$ 25.60
Exercised (in dollars per share)	$ 19.93	[1]
Expired or cancelled (in dollars per share)	$ 0.00
Forfeited (in dollars per share)	$ 19.70
Outstanding at end of the period (in dollars per share)	$ 20.75		$ 19.32
Exercisable, weighted average exercise price (in dollars per share)	$ 20.38	[2]
Vested, exercisable, and expected to vest at end of period, weighted average exercise price (in dollars per share)	$ 20.75	[3]
Weighted-average contractual term
Outstanding at the beginning of the period	8 years 4 months 24 days		8 years 9 months 26 days
Granted	9 years 4 months 29 days
Exercised	7 years 11 months 22 days	[1]
Outstanding at the end of the period	8 years 4 months 24 days		8 years 9 months 26 days
Vested and exercisable at the end of the period	7 years 10 months 29 days	[2]
Vested, exercisable, and expected to vest at end of period	8 years 4 months 24 days	[3]
Aggregate intrinsic value of vested and exercisable options	$ 1.0
Aggregate intrinsic value of vested, exercisable and expected to vest options	$ 3.9

[1] The exercise of stock option awards could result in federal and state income tax expense or benefit related to the difference between the fair value of the stock option award at the date of grant and the intrinsic value of the stock option award when exercised. See Note F for additional discussion regarding the tax impact of exercised stock option awards.

[2] The aggregate intrinsic value of vested and exercisable options at September 30, 2014 was $1.0 million.

[3] The aggregate intrinsic value of vested, exercisable and expected to vest options at September 30, 2014 was $3.9 million.