Goodwill and Other Intangible Assets - Summary of Allocation of Acquisition Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Acquired Finite Lived Intangible Assets [Line Items]
Amortizable intangibles, Gross carrying amount	$ 97,759	$ 97,046
Amortizable intangibles, Accumulated Amortization	63,037	58,060
Goodwill	124,142	121,011	121,011
Customer related intangibles [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Amortizable intangibles, Gross carrying amount	61,325	60,547
Amortizable intangibles, Weighted Average Amortization Period	15 years	15 years
Amortizable intangibles, Accumulated Amortization	33,194	28,864
Acquired software [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Amortizable intangibles, Gross carrying amount	33,103	32,003
Amortizable intangibles, Weighted Average Amortization Period	5 years	5 years
Amortizable intangibles, Accumulated Amortization	28,441	26,584
Trade name [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Amortizable intangibles, Gross carrying amount	3,331	3,109
Amortizable intangibles, Weighted Average Amortization Period	15 years	15 years
Amortizable intangibles, Accumulated Amortization	1,402	1,225
Lease acquired [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Amortizable intangibles, Gross carrying amount		1,387
Amortizable intangibles, Weighted Average Amortization Period		5 years
Amortizable intangibles, Accumulated Amortization		$ 1,387