Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Net income	$ 32,453	$ 18,305	$ 96,027	$ 76,721
Unrealized gains (losses) on marketable securities:
Unrealized holding (losses) gains arising during the period	(37)	796	323	1,363
Reclassification adjustment for gains included in net income	(250)	(1,421)	(480)	(2,107)
Unrealized gains (losses) on marketable securities, net	(287)	(625)	(157)	(744)
Unrealized gains (losses) on interest rate swaps:
Unrealized interest rate swap losses arising during the period	(676)	(2,818)	(704)	(9,982)
Reclassification adjustment for amortization of interest expense included in net income	3,904	5,956	12,046	17,626
Unrealized gains (losses) on interest rate swaps, net	3,228	3,138	11,342	7,644
Foreign currency translation (losses) gains	(3,404)	15,104	(26,461)	7,871
Total other comprehensive (loss) income	(463)	17,617	(15,276)	14,771
Comprehensive income	31,990	35,922	80,751	91,492
Less: comprehensive income attributable to noncontrolling interests	(933)	(805)	(2,839)	(2,379)
Comprehensive income attributable to Alexandria’s common stockholders	$ 31,057	$ 35,117	$ 77,912	$ 89,113