Fair value of financial instruments (Tables)

3 Months Ended

Mar. 31, 2012

Fair value of financial instruments

Schedule of recurring measurements of fair value hierarchy of financial assets and liabilities

	March 31, 2012
	Level 1		Level 2		Level 3		Total
Assets:
Cash and cash equivalents	$	106,609	$	—	$	—	$	106,609
Restricted cash		27,761		—		—		27,761
Derivative instruments asset		—		27,199		—		27,199
Total	$	134,370	$	27,199	$	—	$	161,569
Liabilities:
Derivative instruments liability	$	—	$	159,903	$	—	$	159,903
Total	$	—	$	159,903	$	—	$	159,903

	December 31, 2011
	Level 1		Level 2		Level 3		Total
Assets:
Cash and cash equivalents	$	60,651	$	—	$	—	$	60,651
Restricted cash		21,412		—		—		21,412
Derivative instruments asset		—		32,414		—		32,414
Total	$	82,063	$	32,414	$	—	$	114,477
Liabilities:
Derivative instruments liability	$	—	$	53,762	$	—	$	53,762
Total	$	—	$	53,762	$	—	$	53,762