Intangible Assets - Reconciliation of Goodwill (Detail) $ in Thousands	6 Months Ended
Jun. 30, 2018 USD ($)
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 1,478,380
Goodwill, Ending Balance	1,478,014
Cardinal Financial Corporation [Member]
Goodwill [Line Items]
Addition to goodwill	(366)
Community Banking [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	1,473,265
Goodwill, Ending Balance	1,472,699
Community Banking [Member] \| Cardinal Financial Corporation [Member]
Goodwill [Line Items]
Addition to goodwill	(566)
Mortgage Banking [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	5,115
Goodwill, Ending Balance	5,315
Mortgage Banking [Member] \| Cardinal Financial Corporation [Member]
Goodwill [Line Items]
Addition to goodwill	$ 200

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
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