Stock-based compensation (Tables)

3 Months Ended

Mar. 31, 2018

Executive Officers

Schedule of Unvested Restricted Stock Units Roll Forward [Table Text Block]

(Not in thousands)	Shares		Weighted-Average Grant Date Fair Value
Non-vested at December 31, 2016	383,982	$	26.35
Granted	212,200		42.57
Performance Shares Quantity Adjustment	(232,989)		29.10
Vested	(67,853)		48.54
Non-vested at December 31, 2017	295,340	$	30.75
Granted	157,030		44.70
Performance Shares Quantity Adjustment	106,499		30.37
Vested	(171,636)		36.00
Forfeited	(2,326)		33.07
Non-vested at March 31, 2018	384,907	$	33.98

Directors

Schedule of Unvested Restricted Stock Units Roll Forward [Table Text Block]

(Not in thousands)	Restricted Stock		Weighted-Average Grant Date Fair Value
Non-vested at December 31, 2016	-	$	-
Granted	25,771		38.42
Vested	(25,771)		38.42
Forfeited	-		-
Non-vested at December 31, 2017	-	$	-