Employee Benefit Plans (Defined Benefit Pension Plan Assets at Fair Value) (Detail) - USD ($) $ in Thousands		Dec. 31, 2015		Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value		$ 329,987		$ 339,365
Level 1
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value		203,500		161,912
Level 2
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value		118,555		169,729
Level 3
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value		7,932		7,724
Cash and Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value		3,621		1,101
Cash and Cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value		3,621		1,101
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value		129,633	[1]	154,279	[2]
Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value		83,675	[1]	101,304	[2]
Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value		45,958	[1]	52,975	[2]
Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value	[2]	188,801		110,405
Fixed Income Funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value	[2]	116,204		59,507
Fixed Income Funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value	[2]	72,597		50,898
Other
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value	[3]	7,932		7,724
Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value	[3]	$ 7,932		7,724
Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value	[4]			65,856
Balanced Funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Estimated fair value	[4]			$ 65,856

[1] Investments in passively managed index funds, actively managed mutual funds with holdings in domestic and international equities, and investments in domestic equities. These investments are valued at the closing price reported on the major market on which the individual securities are traded or the Net Asset Value (“NAV”) provided by the administrator of the fund.

[2] Investments in passively managed index funds and actively managed mutual funds with holdings in domestic and foreign corporate bonds, foreign government bonds, mortgage-backed securities, and other fixed income instruments. These investments are valued using matrix pricing models and quoted prices of the securities in active markets.

[3] Investments in a guaranteed deposit fund with holdings in insurance contracts. These investments are valued at contract value of the fund including contributions and earnings, less applicable costs and liabilities, as provided by the administrator of the fund.

[4] Investments in global multi-asset risk parity strategy funds with holdings in domestic and international debt and equity securities, commodities, real estate, and derivative investments. These investments are valued using the NAV provided by the administrator of the fund.