Stockholders' Equity, Stock Repurchase Program (Details) - $ / shares	3 Months Ended		6 Months Ended		210 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Aug. 04, 2015
Stock Repurchase Program [Abstract]
Incremental Class A shares authorized to buyback (in shares)						500,000
Shares repurchased (in shares)	12,532	108,088	43,035	149,481	9,595,688
Average price per share of repurchased shares (in dollars per share)	$ 34.61	$ 72.34	$ 30.93	$ 73.68	$ 44.75
Share available under program to repurchase (in shares)	539,120		539,120		539,120