Earnings per share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Earnings Per Share

The following table represents a reconciliation of the numerator and denominator of the basic and diluted earnings per share computations contained in the consolidated financial statements:

	Year ended December 31,
	2017		2016		2015
	(in thousands, except per share data)
Earnings allocable to Common stockholders	$	24,901	$	11,782	$	—
Earnings allocable to Class A stockholders	$	—	$	13,625	$	21,092
Earnings allocable to Class B stockholders	$	—	$	760	$	1,181
Basic earnings per share:
Common stock	$	1.19	$	0.57	$	—
Class A common stock	$	—	$	0.98	$	1.53
Class B common stock	$	—	$	0.48	$	0.84
Diluted earnings per share:
Common stock	$	1.16	$	0.56	$	—
Class A common stock	$	—	$	0.98	$	1.53
Class B common stock	$	—	$	0.46	$	0.81
Basic weighted average shares outstanding:
Common stock	20,992		20,841		—
Class A common stock	—		13,844		13,796
Class B common stock	—		1,574		1,413
Dilutive effect of shares issued under stock compensation arrangements:
Common stock - stock options	506		232		—
Class B common stock - unvested restricted stock grants	—		70		39
Diluted weighted average shares outstanding:
Common stock	21,498		21,073		—
Class A common stock	—		13,844		13,796
Class B common stock	—		1,644		1,452