Severance and Other Exit Costs - Additional Information (Detail)	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2017 position	Mar. 31, 2017 USD ($) position	Dec. 31, 2014 USD ($) position	Dec. 31, 2016 USD ($)
Employee Severance
Restructuring Cost and Reserve [Line Items]
Severance costs incurred		$ 4,572,000
Accrued reserve		4,297,000		$ 1,559,000
Payments for restructuring		1,834,000
Facilities Closing
Restructuring Cost and Reserve [Line Items]
Facilities charge		1,055,000
Accrued reserve		8,766,000		9,020,000
Payments for restructuring		1,497,000
2014 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | position			90
Severance costs incurred			$ 2,300,000
2014 Restructuring Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Accrued reserve		0
2014 Restructuring Plan | Facilities Closing
Restructuring Cost and Reserve [Line Items]
Future lease payments			3,000,000
Facilities charge		200,000	$ 2,100,000
Payments for restructuring		200,000
Expected cost remaining		200,000
2014 Restructuring Plan | Closing Office Facility in Englewood, Colorado
Restructuring Cost and Reserve [Line Items]
Adjustments relating to lease agreement		$ 0
2016 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | position		265
Severance costs incurred		$ 0
2016 Restructuring Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Accrued reserve		500,000
Payments for restructuring		1,000,000
2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | position	660
Severance costs incurred		4,500,000
2017 Restructuring Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Accrued reserve		3,800,000
Payments for restructuring		700,000
Constant Contact, Inc. | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | position	35
Email Marketing Unit | Employee Severance
Restructuring Cost and Reserve [Line Items]
Severance costs incurred		2,227,000
Accrued reserve		1,960,000		926,000
Payments for restructuring		1,193,000
Email Marketing Unit | Facilities Closing
Restructuring Cost and Reserve [Line Items]
Facilities charge		1,065,000
Accrued reserve		8,561,000		$ 8,747,000
Payments for restructuring		$ 1,251,000