Share-Based Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Statement of Weighted-Average Assumptions Used and Resulting Weighted-Average Fair Value of Option

The following table presents the weighted-average assumptions used and the resulting weighted-average fair value of each option granted for the periods presented.

	2017			2016			2015
Weighted-average risk-free interest rate	2.35		%	1.84		%	1.90		%
Expected dividend yield	—		%	—		%	—		%
Weighted-average expected volatility	25.05		%	23.39		%	21.18		%
Weighted-average expected life (in years)	7.00			7.00			7.00
Weighted-average fair value of each option granted	$	8.68		$	7.61		$	6.42

Summary of Stock Option Activity

The following table summarizes stock option activity for the year ended December 31, 2017:

	Number of Shares		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term in Years	Aggregate Intrinsic Value
(dollars in thousands, except weighted-average exercise price)
Outstanding, December 31, 2016	3,960,040		$	15.25
Granted	776,500		26.92
Exercised	(2,007,762	)	11.30			$	32,029
Expired	(7,334	)	10.91
Forfeited	(2,750	)	17.65
Outstanding, December 31, 2017	2,718,694		$	21.52	7.54	$	12,887
Exercisable at December 31, 2017	96,963		$	12.42	4.06	$	1,317

Summary of Non-Vested Options

A summary of the status of Customers' non-vested options at December 31, 2017, and changes during the year ended December 31, 2017, is as follows:

	Options		Weighted- Average exercise price
Non-vested at December 31, 2016	2,865,962		$	17.24
Granted	776,500		26.92
Vested	(1,017,981	)	12.77
Forfeited	(2,750	)	17.65
Non-vested at December 31, 2017	2,621,731		21.85

Status of Restricted Stock

The table below presents the status of the restricted stock units at December 31, 2017, and changes during the year ended December 31, 2017:

	Restricted Stock Units		Weighted- Average Grant- Date Fair Value
Outstanding and unvested at December 31, 2016	645,505		$	19.43
Granted	218,449		29.93
Vested	(256,078	)	15.70
Forfeited	(17,840	)	25.85
Outstanding and unvested at December 31, 2017	590,036		$	24.74