Debt - Additional Information (Detail) (USD $)	6 Months Ended		6 Months Ended	1 Months Ended	3 Months Ended	6 Months Ended	1 Months Ended		3 Months Ended	6 Months Ended		3 Months Ended
	Jun. 30, 2014 Discretionary Line of Credit	Dec. 31, 2013 Discretionary Line of Credit	Jun. 30, 2014 Discretionary Line of Credit Federal Funds Rate	Apr. 25, 2014 4.35% Senior Notes due 2044	Jun. 30, 2014 4.35% Senior Notes due 2044	Jun. 30, 2014 4.35% Senior Notes due 2044	Oct. 31, 2013 7% Notes due 2013	Jun. 30, 2014 7% Notes due 2013	Sep. 30, 2013 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067	Jun. 30, 2014 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067	Jun. 30, 2013 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067	Sep. 30, 2013 6.70% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 Net unrealized gains on forecasted transactions
Debt Instrument [Line Items]
Debt Instrument, Issuance Date				Apr. 25, 2014
Debt Instrument, Face Amount				$ 350,000,000
Debt Instrument, Interest Rate, Stated Percentage				4.35%	4.35%	4.35%		7.00%		6.70%
Proceeds from Debt, Net of Issuance Costs				346,300,000
Additional Expenses Related to the Issuance				700,000	700,000	700,000
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)				1,600,000
Payment of debt							150,000,000
Repurchase of debt, face amount									54,100,000	0	0
(Gains) losses on extinguishment of debt									4,300,000
Cash flow hedge gain reclassification from accumulated other comprehensive income to net realized gains/losses on securities												800,000
Line of Credit Facility, Maximum Borrowing Capacity	100,000,000	100,000,000
Line of Credit Facility, Interest Rate Description	advances under the Line of Credit (if any) will bear interest at a variable rate equal to the higher of PNC's Prime Rate and the sum of the Federal Funds Open Rate plus 50 basis points.
Line of Credit Facility, Amount Outstanding	$ 0	$ 0
Basis points			0.50%