Acquisitions (Details) (USD $)				12 Months Ended	3 Months Ended		0 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2012 MRM	Dec. 31, 2011 HDI Holdings, Inc.	Mar. 31, 2013 HDI Holdings, Inc. Minimum	Mar. 31, 2013 HDI Holdings, Inc. Maximum	Jun. 30, 2010 Allied Management Group - Special Investigation Unit, Inc item	Mar. 31, 2013 Allied Management Group - Special Investigation Unit, Inc	Dec. 31, 2012 Allied Management Group - Special Investigation Unit, Inc	Jul. 31, 2011 Allied Management Group - Special Investigation Unit, Inc
Business combination
Aggregate consideration			$ 11,800,000	$ 370,400,000			$ 15,100,000
Cash paid for business acquisition			10,800,000	366,600,000			13,000,000
Future contingent consideration			1,000,000
Goodwill			11,200,000
Aggregate fair value of issued replacement option awards				14,300,000
Unvested HDI options being assumed and replaced attributable to purchase price				3,800,000
Vesting period					1 month	48 months
Payment for working capital included in purchase price							200,000
Acquisition related contingent consideration	631,000	588,000					2,300,000
Purchase price due held in escrow and to seller in annual payments							3,500,000
Number of annual payments in which the purchase price is payable							3
Purchase price due to seller in annual payments, year one										1,800,000
Purchase price due to seller in annual payments, year two								875,000
Purchase price due to seller in annual payments, year three								875,000
Annual payments made								1,800,000
Reversal of contingent payment liability									$ 2,300,000