Income Taxes - Additional Information (Detail)	3 Months Ended
Mar. 31, 2013
Income Tax Disclosure [Line Items]
Percentage of REIT taxable income distributed to stockholders	90.00%

Percentage of reit taxable income distributed to stockholders.

No definition available.

Name:	exl_PercentageOfReitTaxableIncomeDistributedToStockholders
Namespace Prefix:	exl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration