Common Stock - (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 05, 2016
Schedule Of Common Stock [Line Items]
Shares repurchased (shares)	4,500,936	8,645,836	6,076,558
Repurchase of shares	$ 93,573	$ 175,048	$ 119,370
Shares outstanding	26,386,583	30,358,509
Common Class A [Member]
Schedule Of Common Stock [Line Items]
Shares outstanding	26,386,583	30,358,509
Restricted issued but not yet vested, shares	499,271	836,031
New Board Authorized Share Repurchase Program
Schedule Of Common Stock [Line Items]
Stock repurchase program, authorized amount				$ 50,000
Remaining authorized amount	$ 12,600