Commitments and contingencies (Tables)

12 Months Ended

Dec. 31, 2013

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, 2013, were as follows (in thousands):

Year	Office Leases		Ground Leases		Total
2014	$	1,324	$	10,520	$	11,844
2015	1,394		9,900		11,294
2016	1,468		10,504		11,972
2017	1,542		10,572		12,114
2018	1,617		10,662		12,279
Thereafter	1,482		635,289		636,771
	$	8,827	$	687,447	$	696,274