Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2016

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 January 1, 2014	585,247	$	21.16
Granted	365,831		29.86
Vested	(311,078)		19.02
Forfeited	(11,991)		29.33
Non-vested at December 31, 2014	628,009	$	27.13
Granted	323,814		33.37
Vested	(430,646)		30.45
Forfeited	(25,446)		28.65
Non-vested at December 31, 2015	495,731	$	28.25
Granted	344,488		25.86
Quantity adjusted by TSR factor	39,566		24.37
Vested	(487,784)		27.72
Forfeited	(8,019)		29.13
Non-vested at December 31, 2016	383,982	$	26.35

Directors

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

(Not in thousands)	Restricted stock		Weighted-average grant date fair value
Nonvested at January 1, 2014	-		-
Granted	23,135	$	30.43
Vested	(23,135)		30.43
Forfeited	-		-
Non-vested at December 31, 2014	-		-
Granted	22,119	$	32.29
Vested	(22,119)		32.29
Forfeited	-		-
Non-vested at December 31, 2015	-		-
Granted	40,517	$	29.77
Vested	(40,517)		29.77
Forfeited	-		-
Non-vested at December 31, 2016	-		-