Fair Value Measurements - Changes in Fair Value Due to Observable Factors (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, Other Assets	$ 17,331	$ 11,390
Total realized gains included in income, Other Assets	558	186
Change in unrealized gains/losses included in other comprehensive income for assets and liabilities still held, Other Assets	0	0
Purchases, issuances and settlements, net, Other Assets	7,654	5,000
Transfers out of Level 3, Other Assets	0	0
Fair value, Other Assets	25,543	16,576
Fair value, Other Liabilities		11,390
Total realized gains included in income, Other Liabilities		186
Change in unrealized gains/losses included in other comprehensive income for assets and liabilities still held, Other Liabilities	0	0
Purchases, issuances and settlements, net, Other Liabilities		5,000
Transfers out of Level 3, Other Liabilities	0	0
Fair value, March 31, Other Liabilities		16,576
Other Liabilities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total realized gains included in income related to financial assets still on the consolidated balance sheet, Other Assets		186
Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total realized gains included in income related to financial assets still on the consolidated balance sheet, Other Assets	$ 558	$ 186