Quarter	Millions of US Dollars
2007-01-01	200
2008-04-01	500
2010-07-01	250
2011-04-01	0
2012-01-01	-200
2012-04-01	250
2012-07-01	1000
2013-10-01	150
2015-07-01	-250
2016-04-01	250
2016-07-01	550
2017-04-01	166
2017-07-01	-500