Common Stock - (Narrative) (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Aug. 05, 2016
Schedule Of Common Stock [Line Items]
Shares repurchased (shares)		1,671,923
Repurchase of shares		$ 32,918
Remaining authorized amount	$ 12,600
Shares outstanding	26,788,833		26,386,583
Common Class A [Member]
Schedule Of Common Stock [Line Items]
Shares outstanding	26,788,833		26,386,583
Restricted issued but not yet vested, shares	256,064		499,271
New Board Authorized Share Repurchase Program
Schedule Of Common Stock [Line Items]
Stock repurchase program, authorized amount				$ 50,000