Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 35,943	$ 32,453	$ 112,808	$ 96,027
Unrealized (losses) gains on marketable securities:
Unrealized holding (losses) gains arising during the period	(2,454)	(37)	13,591	323
Reclassification adjustment for losses (gains) included in net income	111	(250)	517	(480)
Unrealized (losses) gains on marketable securities, net	(2,343)	(287)	14,108	(157)
Unrealized (losses) gains on interest rate swap agreements:
Unrealized interest rate swap (losses) gains arising during the period	1,206	(676)	(2,708)	(704)
Reclassification adjustment for amortization of interest expense included in net income	1,129	3,904	5,742	12,046
Unrealized gains on interest rate swap agreements, net	2,335	3,228	3,034	11,342
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(12,259)	(3,404)	(9,450)	(26,461)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	(199)	0	(199)	0
Foreign currency translation gains (losses)	(12,458)	(3,404)	(9,649)	(26,461)
Total other comprehensive income (loss)	(12,466)	(463)	7,493	(15,276)
Comprehensive income	23,477	31,990	120,301	80,751
Less: comprehensive income attributable to noncontrolling interests	(1,340)	(933)	(3,842)	(2,839)
Comprehensive income attributable to Alexandria’s common stockholders	$ 22,137	$ 31,057	$ 116,459	$ 77,912