Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Net income	$ 33,337	$ 25,641	$ 63,574	$ 58,416
Unrealized gains (losses) on marketable securities:
Unrealized gains (losses) on marketable securities:	44	(107)	360	567
Reclassification adjustment for (gains) losses included in net income	42	238	(230)	(686)
Unrealized gains (losses) on marketable securities, net	86	131	130	(119)
Unrealized gains (losses) on interest rate swaps:
Unrealized interest rate swap gains (losses) arising during the period	105	(3,091)	(28)	(7,164)
Reclassification adjustment for amortization of interest expense included in net income	3,834	5,895	8,142	11,670
Unrealized gains (losses) on interest rate swaps, net	3,939	2,804	8,114	4,506
Foreign currency translation losses	(20,698)	(17,192)	(23,057)	(7,233)
Total other comprehensive income	(16,673)	(14,257)	(14,813)	(2,846)
Comprehensive income	16,664	11,384	48,761	55,570
Less: comprehensive income attributable to noncontrolling interests	(1,008)	(875)	(1,906)	(1,574)
Comprehensive income attributable to Alexandria’s common stockholders	$ 15,656	$ 10,509	$ 46,855	$ 53,996