Merger, Acquisition and Other Integration Expenses - Schedule of Merger Acquisition and Integration Expenses (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Business Acquisition [Line Items]
Termination, severance and transitional employee costs	$ 54,283	$ 58,445
Professional fees	17,599	46,467
Office closure, travel and other costs	8,794	24,714
Write-off of deferred loan costs		10,869
Total	$ 80,676	$ 140,495	$ 0