Fair Value Measurements - Changes in Fair Value Due to Observable Factors (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, Other Assets	$ 26,672	$ 17,331
Total realized gains included in income, Other Assets	124	$ 392
Change in unrealized gains/losses included in other comprehensive income for assets and liabilities still held, Other Assets	0
Purchases, issuances and settlements, net, Other Assets	210	$ 7,402
Transfers out of Level 3, Other Assets	0	0
Fair value, Other Assets	27,006	25,125
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total realized gains included in income related to financial assets and liabilities still on the consolidated balance sheet	124	392
Other Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, Other Liabilities	0	0
Total realized gains included in income, Other Liabilities	0	0
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	0	0
Transfers out of Level 3, Other Liabilities	0	0
Fair value, Other Liabilities	0	0
Total realized gains included in income related to financial assets and liabilities still on the consolidated balance sheet	$ 0	$ 0