Commitments and Contingencies - Commitments and Letters of Credit (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Commitment And Contingencies [Line Items]
Commitments and letters of credit	$ 1,195,938	$ 1,117,168
Commitments to Extend Credit [Member]
Commitment And Contingencies [Line Items]
Commitments and letters of credit	1,117,511	1,038,529
Standby Letters of Credit [Member]
Commitment And Contingencies [Line Items]
Commitments and letters of credit	$ 78,427	$ 78,639