Stock-Based Compensation Plans (Tables)

3 Months Ended

Mar. 31, 2018

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

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

The following table summarizes the Company’s stock option activity for the three-month period ended March 31, 2018:

					Weighted
			Weighted		Average
			Average		Remaining		Aggregate
			Exercise		Contractual		Intrinsic
	Shares		Price		Term (Years)		Value*
Outstanding at December 31, 2017		1,502,493	$	26.57
Exercised		(107,743)	$	26.76
Forfeited or expired		(11,575)	$	26.52
Outstanding at March 31, 2018		1,383,175	$	26.56		3.7	$	9,744,000
Exercisable at March 31, 2018		769,388	$	26.57		2.1	$	5,412,000

* The aggregate intrinsic value of outstanding and exercisable stock options is defined as the difference between the market value of the Company's stock on March 29, 2018, the last trading day of the quarter, of $33.60 and the exercise price multiplied by the number of in-the-money outstanding and exercisable stock options.

Share-based Compensation, Stock Options Exercised, Activity [Table Text Block]

The following table summarizes the Company’s stock option exercise activity for the three months ended March 31, 2018 and 2017:

	Three Months Ended March 31,
	2018		2017
	(Dollars in thousands)
Total intrinsic value of stock options exercised	$	501	$	41
Cash received from stock option exercises	$	2,884	$	356
Income tax benefit from the exercise of stock options	$	130	$	15

Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]

The following table summarizes the Company’s restricted stock award activity for the three-month period ended March 31, 2018:

					Weighted
			Weighted		Average
	Shares of		Average		Remaining		Aggregate
	Restricted		Grant Date		Contractual		Intrinsic
	Stock		Fair Value		Term (Years)		Value*
Non-vested at December 31, 2017		66,050	$	26.79
Issued		-		-
Vested		-		-
Forfeited		(1,675)		26.59
Non-vested at March 31, 2018		64,375	$	26.80		2.6	$	2,163,000

* The aggregate intrinsic value of non-vested restricted stock was calculated using the market value of the Company's stock on March 29, 2018, the last trading day of the quarter, of $33.60 multiplied by the number of non-vested restricted shares outstanding.