Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share Disclosure [Line Items]
Net income attributable to XO Group Inc.	$ 1,673	$ 397
Total weighted-average basic shares	24,460,000	25,519,000
Dilutive securities:
Total weighted-average diluted shares	25,254,000	26,092,000
Net income per share attributable to XO Group Inc. common stockholders:
Basic (usd per share)	$ 0.07	$ 0.02
Diluted (usd per share)	$ 0.07	$ 0.02
Out of Money
Net income per share attributable to XO Group Inc. common stockholders:
Weighted average number of antidilutive stock options and restricted stock excluded from the calculation of earnings per share (shares)	0	162,779
Restricted stock
Dilutive securities:
Dilutive securities (shares)	665,000	450,000
Employee Stock Purchase Plan
Dilutive securities:
Dilutive securities (shares)	7,000	8,000
Options
Dilutive securities:
Dilutive securities (shares)	122,000	115,000