Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of reconciliation of the numerators and denominators used in the basic and diluted per-share computations

A reconciliation of the numerators and denominators used in the basic and diluted per-share computations is presented as follows for each class of common stock:

(dollars in thousands, except per share data)						For the years ended December 31,
	2017					2016					2015
	Allocated net income (numerator)		Weighted shares (denominator)	Per- share amount		Allocated net income (numerator)		Weighted shares (denominator)	Per- share amount		Allocated net income (numerator)		Weighted shares (denominator)	Per- share amount
Class A – Basic EPS:
Income available to  Class A stockholders	$	195,386	46,186,831	$	4.23	$	208,644	46,188,952	$	4.52	$	173,248	46,186,671	$	3.75
Dilutive effect of stock-based awards	0		49,832	—		0		145,551	—		0		211,340	—
Assumed conversion of Class B shares	1,613		6,100,800	—		1,722		6,100,800	—		1,430		6,100,800	—
Class A – Diluted EPS:
Income available to Class A stockholders on Class A equivalent shares	$	196,999	52,337,463	$	3.76	$	210,366	52,435,303	$	4.01	$	174,678	52,498,811	$	3.33
Class B – Basic EPS:
Income available to Class B stockholders	$	1,613	2,542	$	635	$	1,722	2,542	$	678	$	1,430	2,542	$	563
Class B – Diluted EPS:
Income available to Class B stockholders	$	1,613	2,542	$	634	$	1,721	2,542	$	677	$	1,429	2,542	$	562