Quarter	Millions of US Dollars
2006-01-01	2561
2006-04-01	8174
2006-07-01	18047
2006-10-01	15089
2007-01-01	6987
2007-04-01	12488
2007-07-01	6511
2007-10-01	5210
2008-01-01	6837
2008-04-01	6014
2008-07-01	5509
2008-10-01	7169
2009-01-01	11005
2009-04-01	8553
2009-07-01	8146
2009-10-01	-3862
2010-01-01	10493
2010-04-01	5924
2010-07-01	2448
2010-10-01	4764
2011-01-01	16324
2011-04-01	20110
2011-07-01	15177
2011-10-01	9409
2012-01-01	17632
2012-04-01	11272
2012-07-01	16705
2012-10-01	1547
2013-01-01	19015
2013-04-01	11801
2013-07-01	8943
2013-10-01	13185
2014-01-01	16736
2014-04-01	10883
2014-07-01	10097
2014-10-01	8590
2015-01-01	13022
2015-04-01	4462
2015-07-01	4827
2015-10-01	622
2016-01-01	-1238
2016-04-01	-12614
2016-07-01	10360
2016-10-01	1027
2017-01-01	12847
2017-04-01	8526
2017-07-01	10269
2017-10-01	-4773
2018-01-01	8012