Acquisitions - Additional Information (Detail) In Millions, unless otherwise specified	1 Months Ended	6 Months Ended	12 Months Ended	1 Months Ended	6 Months Ended
	Dec. 31, 2012 Senn Delaney [Member] USD ($)	Jun. 30, 2013 Senn Delaney [Member] USD ($)	Dec. 31, 2012 Senn Delaney [Member] USD ($)	Mar. 31, 2010 Bell McCaw Bampflyde Limited [Member] NZD	Jun. 30, 2013 Bell McCaw Bampflyde Limited [Member] USD ($)	Jun. 30, 2012 Bell McCaw Bampflyde Limited [Member] USD ($)	Jun. 30, 2011 Bell McCaw Bampflyde Limited [Member] USD ($)	Jun. 30, 2013 Bell McCaw Bampflyde Limited [Member] NZD
Business Acquisition [Line Items]
Consideration paid to purchase	$ 53.5		$ 53.5	0.8	$ 0.6
Percentage of equity of acquired company	100.00%		100.00%
Additional cash consideration	15.0		15.0					1.4
Specific earnings milestones achieved period			3 years
General and administrative expense of acquisition related costs		1.0
Retention escrow paid	6.5	6.5	6.5
Minimum service period acquired to cover under plan		3 years	3 years
Compensation expense		1.2
Acquisition Date	Dec. 31, 2012			Mar.01,2010
Earnout payments for acquisitions					$ 0.4	$ 0.4	$ 0.4