Acquisitions - MDA Holdings Narrative (Detail) (USD $)	12 Months Ended						3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010 MDA Holdings Inc [Member]	Dec. 31, 2013 MDA Holdings Inc [Member]	Dec. 31, 2012 MDA Holdings Inc [Member]	Jun. 30, 2009 Related to the 2008 performance [Member]	Jun. 30, 2010 Related to the 2009 performance [Member] MDA Holdings Inc [Member]
Business Acquisition, Contingent Consideration [Line Items]
Release from escrow account				$ 3,541,000
Remaining escrow deposit balance					3,566,000	3,566,000
Payments to acquire businesses net of cash acquired	$ 28,700,000	$ 0	$ 0				$ 6,748,000	$ 12,826,000