Commitments and contingencies (Tables)

12 Months Ended

Dec. 31, 2014

Commitments and Contingencies Disclosure [Abstract]

Schedule of future minimum lease obligations under non-cancelable ground and other operating leases

Future minimum lease obligations under non-cancelable ground and other operating leases as of December 31, 2014, were as follows (in thousands):

Year	Office Leases		Ground Leases		Total
2015	$	1,501	$	9,828	$	11,329
2016	1,490		10,436		11,926
2017	1,561		10,506		12,067
2018	1,632		10,595		12,227
2019	2,115		8,978		11,093
Thereafter	—		616,739		616,739
	$	8,299	$	667,082	$	675,381